Smell of Attraction and Ovulation

Ovulation is the stage during a women’s menstrual cycles when the ovaries release an egg. Although the process is not visible, it has been shown that men are not only able to smell, but are more attracted to women when they are ovulating. In one study, one group of men smelled T-shirts that were worn by women nearing ovulation and another group smelled shirts from when women were far from ovulation. Men that were exposed to the scent of ovulating women displayed higher levels of testosterone than the non ovulating scent. This shows that olfactory cues that detect sexual availability in women are associated with endocrinological responses in men, which can subsequently drive their sexual behavior. 

https://academic.oup.com/beheco/article/15/4/579/205993