Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
The human brain doesn't stop developing until about 25 years old.
102
Your heart will pump about 212 million liters in its lifetime.
26
Your body is creating and killing about 2.4 million red blood cells per second.
17
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
The average person's skin weighs twice as much as their brain.
131
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515