Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
When you get goosebumps and your hair stands, the hair helps to trap air, making you feel warmer by keeping in your body heat.
46
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
If you are cold you are more likely to be hungry because you use energy to keep warm.
143
Your heart will pump about 212 million liters in its lifetime.
26
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
It takes about 20 seconds for a red blood cell to circle the whole body.
102