For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
The average person's skin weighs twice as much as their brain.
131
Enamel is hardest substance in the human body.
61
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
Chewing gum boosts your brain power.
285
The human brain doesn't stop developing until about 25 years old.
102
The average sperm cell swims at 8 inches per hour.
76
It takes about 20 seconds for a red blood cell to circle the whole body.
102