We know some animals and insects use pheromones to attract mates. Do humans?
One affirmative sign is the growing trend of pheromone parties, where singles submit a t-shirt they've slept in for three consecutive nights so that other attendees can pick the scent that's attractive to them.
Tell us what you think below, and watch the full story - including a pheromone party in Houston - on "20/20: Crazy, Stupid Love" Friday at 10 p.m. ET.