Enamel is hardest substance in the human body.
61
It takes about 20 seconds for a red blood cell to circle the whole body.
102
The human brain doesn't stop developing until about 25 years old.
102
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The human brain is very soft, having a consistency similar to soft gelatin or firm tofu.
13
Staying awake for 17 hours is the same for your body as drinking 2 glasses of wine.
193
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18