How to unlock: Talk to Neriah on the upper deck of the Prydwen ship (M7,2).
Neriah can be found on the upper deck of the main ship Prydwen. She is conducting a research and she needs blood samples of various species. The only way of getting them is looting the bodies of all enemies you defeat. Whenever you find a sample, return to Neriah and give it to her for some bottlecaps.
Quest rewards: bottlecaps.