Amniotic fluid

Amniotic fluid was a liquid which, according to the Fourth Doctor, "life [came] from" through a process wherein "the amino acids [fused] to form minute cells. Cells which eventually [evolved] into vegetable and animal life."

When Scaroth tried to take off from the Atlantic Ocean in his ship, its systems failed and the resulting crash released radiation which reacted with the fluid present in the ocean, creating life on Earth. (TV: City of Death)

The Moon also had amniotic fluid, because inside the Moon, there was a creature, waiting to hatch. (TV: Kill the Moon)