In DS9 the Changelings are shown in two different ways. Initially Odo is shown to have grown from a child to an adult indicating that each Changeling has its own distinct physical body. In later episodes, when the homeworld is visited, it is shown that the Changelings exist in their natural form as a large planet size goo and can then leave that to form a body for talking to and interacting with others.
Has it ever been explained what a Changeling actually is? When they meld, are they still two distinct physical forms with their own genetic makeup and therefore have to physically be in the place they emerge from the goo, or are they a collection of separate consciousnesses that "borrow" some of the physical matter that makes up their world to make a body and may never take the same material twice?