Ross: It was a hug!
Phoebe: Okay, just tell me this... did you or did you not smell her hair?
Ross: Smell her hair? ...What if I did?
Phoebe: Ninety percent of a woman's pheromones come out the top of her head! That's why, that's why women are shorter, so that men will fall in love when they hug them! C'mon Ross, you're a scientist!