Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
When you take a step, you are using up to 200 muscles.
886
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
197
The human brain uses approximately as much energy as a 10 watt light bulb.
120
The human brain doesn't stop developing until about 25 years old.
102