Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The average sperm cell swims at 8 inches per hour.
76
Your body is creating and killing about 2.4 million red blood cells per second.
17
Dogs can be trained to identify the scent of lung cancer long before symptoms develop.
190
Chewing gum boosts your brain power.
285
The human brain doesn't stop developing until about 25 years old.
102
Your thumb is about the same size as your nose.
124