Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Yawns are more contagious among people with closer relationships.
163
The average sperm cell swims at 8 inches per hour.
76
Your body is creating and killing about 2.4 million red blood cells per second.
17
Your thumb is about the same size as your nose.
124
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
If your DNA was stretched out it would reach to the moon 6,000 times.
256