Enamel is hardest substance in the human body.
61
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
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
Your body is creating and killing about 2.4 million red blood cells per second.
17
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 average sperm cell swims at 8 inches per hour.
76