It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
The average sperm cell swims at 8 inches per hour.
76
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
Enamel is hardest substance in the human body.
61
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
It takes about 20 seconds for a red blood cell to circle the whole body.
102
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118