Yawns are more contagious among people with closer relationships.
163
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Enamel is hardest substance in the human body.
61
Every year your body replaces 98% of your atoms.
119
The human brain doesn't stop developing until about 25 years old.
102
It takes about 20 seconds for a red blood cell to circle the whole body.
102
Your body is creating and killing about 2.4 million red blood cells per second.
17