To nitpick means to do something with excessive attention to detail. Literally nitpicking refers to combing through hair to find nits, or the eggs laid by lice, something that requires attention to detail. Someone who is "nitpicky" comments on or finds fault with every problem or error, no matter how small.

nitpick(v) = do something (check, question,...) in details so much. We can get nitpicky = we can get in details.