For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
Yawns are more contagious among people with closer relationships.
163
Enamel is hardest substance in the human body.
61
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Every year your body replaces 98% of your atoms.
119
The human brain doesn't stop developing until about 25 years old.
102