In Age of Ultron when
Ultron and Dr. Helen Cho were creating the body that would become the Vision, she stated that the Vibranium was bonding with "the organic material".
Where did this material come from and and whose material was it?!
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While she was perfectly capable of using her technology to replicate a person's personal flesh and DNA signature, she did state she could create new flesh using her cradle's technology.
This means there was no need for a known donor. Either the flesh was cloned from some unknown person or it was created using whatever the nature of the process she had invented.
This would jibe with the Vision's synthetic body in the Marvel Canon Universe, Earth-616, where his body was artificially created and given powers through some undisclosed process.