Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Your heart will pump about 212 million liters in its lifetime.
26
Enamel is hardest substance in the human body.
61
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
One human hair can support 3 ounces.
191
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
Your body is creating and killing about 2.4 million red blood cells per second.
17