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
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
Yawns are more contagious among people with closer relationships.
163
One human hair can support 3 ounces.
191
An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73
If you are cold you are more likely to be hungry because you use energy to keep warm.
143
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515