The male reproductive system is a fascinating area of the human anatomy and is home to some pretty interesting little tidbits of information. For example, did you know most men deal with an average of 11 boners each day, three to five of which occur during the night? Men actually start experiencing boners before they are even born. Male fetuses start producing fetal erections as early as 16 weeks into their mother’s pregnancy.

What may surprise you most is that all boners are not one in the same. In fact, men experience three different types of erections. The first is reflexogenic, which is an erection resulting from physical contact. The second is psychogenic or an erection caused by a fantasy. The third is nocturnal or an erection that occurs when men are in their REM cycle of sleep.

In order for a penis to “get hard,” it requires around 130ml of blood. What can increase that blood blow? Chicago’s Smell and Taste Treatment and Research Foundation revealed in 1955 that the smell of doughnuts and black licorice increased blood flow to the penis by 32 percent. What decreases blood flow and increases a man’s risk for erectile dysfunction? Smoking.

Correction: A previous version of this article incorrectly stated that fetal erections can begin as early as 16 months into pregnancy. In fact, they can begin as early as 16 weeks into pregnancy.