Dib: You know Zim, when the nurse examines you, she'll notice that you don't have human organs. Then it's just a short step to a hospital and from there to an alien autopsy table and then you're just another segment on "Mysterious Mysteries"!

-Invader Zim: Dark Harvest

As I understand it, Superman was originally supposed to basically be the equivalent of a human who had developed under immense gravity - giving him extraordinary strength. Of course, that has all changed over the years and Superman gained powers like actual flight, heat and x-ray vision, invulnerability and the ability to disguise himself with nothing but a pair of glasses and fixing his hair.

I also seem to recall an episode of Smallville where Clark realizes that he had never been sick or injured as a child.

One must assume that he has something different about his eyes to shoot heat vision or use x-ray vision. So, just how different is Superman's physiology from that of a human? Does he have the same organs and skeletal/muscle structure? Is his heart where our stomach is? Does he have an appendix?

  • 6
    Superman has 5 hearts and a squiggly-spooch. Apr 9, 2013 at 14:45
  • 2
    But does he have head pigeons?
    – phantom42
    Apr 9, 2013 at 14:47
  • @GorchestopherH I was going to say he had the cold dead heart of a Kryptonian. Apr 9, 2013 at 15:32
  • @GorchestopherH - squiggly-spooches are unscientific. Apr 10, 2013 at 15:57
  • 2
    @DVK To puny human science, perhaps. Apr 10, 2013 at 21:01

4 Answers 4


The short answer: Superman and Kryptonians in general, only share one characteristic with human beings; our external physical, bilaterally symmetrical appearance. Kryptonians sufficiently resemble Humans enough for them to be able to pass as Human but only from a cursory physical inspection. Any trained medical personnel should be able to determine a Kryptonian is not Human with only a modest toolkit of scientific equipment.

The Long Answer: DC Comics has never given us a cohesive or guided tour into Superman's physiology over the decades of his existence. Supposedly born on a world with gravity far greater than Earth's, Kryptonians were thought to have incredible physical capabilities including superhuman levels of strength, durability and stamina. Superman as a biological entity is almost implausible given the parameters of his abilities in the comics.

Given his creators, Jerry Siegel and Joe Shuster were not scientists in the 1940s, his powers were very loosely defined as:

  • faster than a speeding bullet
  • more powerful than a locomotive
  • able to leap tall buildings in a single bound
  • nothing less than a bursting shell could even pierce his skin

Under these parameters, Kryptonians were later thought to be very advanced humanoids externally very similar to Humans. The internal workings, however, had to be vastly different to allow them to do even these relatively simple feats able to be done by the Golden Age (Earth-2), Pre-Crisis Superman.

The Golden Age Superman (and the only version which has any modicum of a chance to be remotely physically possible) had to be a specimen of incredible physical capability to perform even his relatively limited suite of super feats:

  • Due to his denser muscle and bone tissues he was able to resist small arm fire and was nearly invulnerable to conventional injuries.

  • His denser musculature allowed him to be able to move far greater weights than any human possible could and allowed him to run as fast as a moving automobile or jump as high as a fifty story skyscraper.

  • Born to a world with a stronger gravity, under Earth's gravity, Superman's reflexes are many times faster than ours, able to even catch a bullet in mid air.

Unfortunately, modern science cannot replicate or explain how Superman was able to perform these relatively modest superhuman feats without a significant restructuring of both his chemical processes and his physical structure.

I have in the past tried to rationalize his powers but the underlying energy source to explain how he powers his superfeats defies scientific description. We are forced to rely on handwaving of the laws of physics to explain how he:

  • absorbs solar energy into his body and stores it for later use. How is the energy stored, chemically, as radioactivity, as a matter-antimatter reaction?

  • being a man-sized body, he cannot possible absorb enough solar energy to perform even one of his average feats of superhuman ability. Where does the rest of the energy come from?

  • can carry objects much larger than he is and they don't fall apart when he picks them up? If he is a telekinetic, that might explain some of the superfeats in terms of their physics-defying nature, but we then must explain the telekinetic ability as well.

  • is able to perform any of his modern feats at all. If his powers are purely a physical representation of how his body processes energy, his organs would bear no resemblance to anything human. He would be suffused with a variety of both organs and cellular structures completely different from anything human. They would need to be since his energy profile would be so far removed from anything human. He is human in appearance only. Viewing him under any kind of scanning technology should show a creature as different from us as we are from viruses.

As far as his eyes and other sensory abilities:

  • they too would seem to be better explained as psionic abilities rather than physical abilities, since it would imply his eyes are capable of absorbing and processing far more light than our eyes can, even though they are the exact same size as human eyes.

  • Greater muscular strength and precise muscle control might explain the increase acuity of his microscopic and telescopic visions but his abilities exceed that of our greatest machines, its more like magic than science.

  • The use of heat vision capable of reaching 6,000 degrees as an energy being released from his eyes would imply his eye structures are as different from our eyes as any organ can be. Again, better explained as a form of psychic ability than a physical one.

I am relatively certain, given Superman's abilities, the longevity of the character, and the currently undisclosed nature of his biology, it is safe to assume we will never be given a full disclosure of his anatomy for one simple reason.

Once you define it, there will be people who will want to go back through history and see if the definition has been exceeded. Since we accept Superman's outrageous history as fact (as defined by DC Comics) it is simply easier for them to leave it undefined than to have to retroactively explain how he did any of those feats in the first place.

I created a profile of Pre-Crisis Earth-1 Superman's physiology and an explanation of his powers back in the late 1990s on my website the Starnet Metahuman Information Database. This was back before the comic industry had begun posting their heroes online. Only the Wayback Machine can get us there now. Enjoy the link...

  • 1
    A good summary of Superman from 1938 and beyond. Enjoyed your analysis of his physiology. You may enjoy Mark Wolverton's The Science of Superman (2002). I gave a talk on Superman's powers, the Silver Age Superman, and hand-waved my way through an outrageous amount of exotic science. Good to see others doing research into this challenging topic.
    – a4android
    Nov 1, 2019 at 6:49
  • I tell people how inhuman he is and they don't believe me. On the other hand, he can mate with humans -- can a virus do that?
    – releseabe
    Feb 28, 2023 at 21:35

Believe it or not, this is something I've given some significant thought to...and, brazen as it may be, I think both the Post-and Pre-Crisis reasoning are actually...not wrong, but lacking in correctness, a bit. I just never bought that he gets "all" his powers from the yellow sun, full stop.

Most comics touch on the 2 big reasons for Superman's abilities, which everyone knows about:

1] The Gravity

2] Earth's Yellow sun.

I postulate that there is a third reason, which essentially goes back to his vastly different Kryptonian physiognomy, not just his cell structure.

In a 2000 reprint Millennium edition of Superman #1, 1939 , it reads that Clark's main powers, as evidenced on one 8-panel page are that he could...

Hurdle sky scrapers, Leap an 8th of a mile, run faster than a streamline train and nothing less than a bursting shell could penetrate his skin!

Later pages in this same book, a page offers _"Scientific Explanation for Superman's Amazing Strength--!" saying that:

Superman came to earth from KRYPTON, whose inhabitants had evolved, after millions of years, to physical perfection....The smaller size of our planet, with its slighter gravity pull, assists Superman's tremendous muscles in the performance of miraculous feats of strength!...Even upon our world Today exist creatures possessing SUPER STRENGTH! The lowly ant can support weights hundreds of times its own. The grasshopper leaps what to a man would be the space of several city blocks!"

And lastly....

"It is not too far-fetched to predict that someday, our very own planet may be peopled entirely by SUPERMEN!"

A story in said-same reprint goes on to elaborate at other points of his different structure and indestructibility. An accident occurs in a mine shaft, where "poison gas" is released. Superman enters into the shaft freely, "his physical structure unaffected by the gas"...

This hints that his muscles, nerves and cells on a whole are so far advanced they are highly resistant, if not invulnerable to toxic fumes as well as terrific physical force. A written portion in this same book, penned by Jerry Siegel, recounts: "....

...with amazing rapidity, he stripped off his glasses and outer garments, revealing himself clad in a close fitting costume and flaring cape. In this apparel, it was apparent that he really possessed a fine physique of breathtaking symmetry. One lithe leap brought him to the window sill. There, he poised momentarily while his keen telescopic vision surveyed the vicinity

So apparently, the Pre-Crisis account of near physical "perfection" accounted for super strong senses, as well [at least telescopic, if not microscopic & x-ray vision]. This goes to what I consider the 3rd, base source of at least a portion Superman's powers

3] Highly advanced Kyrptonian physiology, that is, in some ways, deeply different from humans.

Oh, it maybe humanoid, yes, but not completely human in any fundamental way, other than its exterior design. Now granted, everything I'm putting forth here is somewhat speculative; there have been only occasional references to any of these elements in the canon comics. As such, most of this is put forth via observation. As such, the differences in a Kryptonian body which we may deduce contribute to this physiology are as follows.

1. A more evolved form of muscle cells and tissues, combining both slow-twitch AND fast-twitch properties. These "pink muscles" would allow Superman to produce a greater amount of force, without tiring , and for far longer periods. They would also probably have a naturally higher number of mitochondria [the cellular powerhouses] which would produce greater contraction ratings in each fiber. In other words, if there was no yellow sun and equal gravity, and Superman was placed against an earthling of equal size, height, weight and mass, his muscles would still work, on average, 10-20 times better and longer, making him an average of possibly 20 times stronger.

2. A cell structure that more efficiently copies itself, allowing the cells to flush toxins, renew themselves and make perfect clone cells without [or at least with a highly retarded rate of] degradation. This would mean every cell in his body, even without a yellow sun, produces less waste chemicals from break down, and more quickly reproduces/regenerates itself from damage. This would essentially give Superman a "healing factor" or sorts, as he would not easily sustain major tissue damage. He would also, consequently, age more slowly.

3. A corded muscle structure. Most human muscle is smooth and flat; it's possible Kryptonians have muscles which are linked like braided ropes or chains, meaning the fibers are entwined in a latices pattern. This phenomenon is real, and can be seen in other bipeds, like simians, who, pound for pound, are stronger than humans of equal weight. This would naturally make them stronger and more durable, physically.

4. Adaptive antibodies in his immune system. Superman's immune system would need to be more evolved to be able to "resists poisons" as he does, or at least allow his structure to adapt to said poisons better than ours do. It's likely that the harsher Kryptonian environment produced "super bugs" which his immune system developed normal defenses for, so anything from this planet wouldn;t even register as a threat to it.

5. A more advanced chromosomal structure. Consdiering there is only a 10% difference between the DNA of a virus, and that of a human, yet we are radically different in some ways, it's not illogical to think Kryptonian physiology is different on a chromosomal level. So even in terms of chromosomal development or possible number, on the fundamental level where new genes are created, Superman's body has a natural edge after thousands more years of evolution. These chromosomes would also account for the organelles in his cell structure which absorb, condense and store solar radiation, allowing for the photo-voltaic affect which allows him to produce even MORE physical power.

Bonus: Chromosomal differences would also easily explain why Superman simply can't have a child with an earth woman; we're vastly different, even at the genetic level.

6. A more advanced neuro-synaptic structure, which accounts for Superman's greater memory, senses, and faster nervous system, while also attributing in part to his strength and speed. Logically, his nerves would need to fire faster to power more evolved muscle tissue at a greater rate. This likely also means that Superman largely perceives everything around him in "slower motion" than most humans, and, without the sun, he would likely still be capable of moving & thinking between 40 - 90 times faster than an average person

8. Greater abundance of stem or progenitor cells, which would also mean greater capacity for developed sensory cells. Where as a human has 2 million odor sensitive cells in his nose, Superman might have 20-10,000 times more, for instance; same thing for his sense of sight, taste, touch....even some senses we might not know about. This would explain his vision, even for him being able to see in the entire spectrum; many earth animals already see outside visible light spectrum, yet their eyes aren't "super" evolved.

9. Actual development of new regions in the brain, or greater access to all regions. The prefrontal cortex is really the central structure in the human brain which accounts for our higher development compared to most other species. Taking it a step further in Kryptonian bodies, their brains may have developed regions which can allow for psionic abilities, such as telepathy, eidetic memory, and limited telekinesis. This telekinesis would need to be amplified by energy from the yellow sun (else only done via extreme concentration). This would be one way to account for Superman's ability to fly under a yellow sun; the only other option is some form of graviton manipulation via some new organ.

10. Personal gravitational control organ. Lex Luthor theorized this in Superman: Birthright, and it makes sense. It's basically some type of internal structure or structures, like lymph nodes, which control a personal gravity field would allow him to [a] fly at will with enough energy to control it, [b] maintain his molecular density on this or any other lighter planet [c] explain why his body "instinctively" stays "planted" on earth, as opposed to Superman moving on earth the way a human moves on the moon, and why his muscle doesn't waste away while being on this planet.

All of these would be latent, normal abilities ANY Kryptonian would have on their planet, just on comparatively LOWER levels; this would, largely, be the result of that planet's gravity, environment, atmosphere and cosmology....as well as perhaps a comparatively quicker rate of their race's evolution weeding out many of their weaknesses.

So, on a super-giant world like Kyrpton, which could easily be 50 times earth's size or more, and theoretically made of even heavier materials.... these abilities are fairly common. While "super", yes, they are by no means God-like due to the planet itself "limiting" their ability, and the lack of a super-empowering Yellow sun. If on the other hand, they had a yellow sun on Krypton, their physiology would be super energized, but perhaps still affected by the gravity & environment of the world, making them....mmmm, perhaps 1/3 - 1/10 as strong as Superman in an Earth environment is.

On Earth proper, however, under "0.03 standard Kryptonian Gravity" [Superman: Birthright #1 2002], and with the cellular enhancing power of the yellow sun multiplying this increase by a factor of anywhere from 100 to 1,000,000,000 its not inconceivable that his latent abilities would ALSO be enhanced to such levels, making him be able to move continents with ease, think at speeds faster than light, and counteract our gravity completely by telekinetically "propelling" himself through space.

Again, though, this is mostly conjecture.

  • 1
    I refer you to Mark Wolverton's book The Science of Superman (2002). It's a reasonable attempt to scientifically rationalize Superman, his powers and abilities.
    – a4android
    Nov 1, 2019 at 6:37
  • @a4android didn't they make a documentary on this at one point?
    – Russhiro
    Nov 1, 2019 at 12:45
  • Yes, that's right. I believe it even had the catchy title of The Science of Superman.
    – a4android
    Nov 3, 2019 at 11:17

Kryptonians have an organ in their body.It is called a Bio-Matrix.It stores the solar energy he has absorbed over the years and users it to fuel his metabolism as well as abilities.Superman can survive without food and water because he does not need the energy from it as the energy stored in his bio-matrix serves the purpose.Humans do not posses a bio-matrix and hence need food and water for survival and evolution.

  • 5
    Do you have a reliable source or citation to back this up?
    – phantom42
    May 17, 2016 at 15:52
  • This is comic book science. From memory the immediate era of the John Byrne incarnation of Superman gave hand-wavey "explanations" of the bio-matrix as a sort of force-field surrounding his body. Somehow this gave Superman his super-powers. Whatever somehow means in this context.
    – a4android
    Nov 1, 2019 at 6:33

As far as we know the only difference between Super Man and Humans is Blood. When us 'Humans' study clarkes blood we only notice the colouration change with its exposure to kryptonite. With deeper research you may be able to find exactly what differences there are to physiology and blood and make the changes to yourself. Now that i think about it... someone is probably already trying that

  • Between the misspellings and the rambling, I don't feel like this makes for a good answer. That said, it's also over three years old...
    – FuzzyBoots
    May 17, 2016 at 16:03

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