Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
The average person's skin weighs twice as much as their brain.
131
Enamel is hardest substance in the human body.
61
Your thumb is about the same size as your nose.
124
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
The human body contains over a billion miles of DNA.
147
The average sperm cell swims at 8 inches per hour.
76