Yawns are more contagious among people with closer relationships.
163
It takes about 20 seconds for a red blood cell to circle the whole body.
102
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
The average sperm cell swims at 8 inches per hour.
76
When you get goosebumps and your hair stands, the hair helps to trap air, making you feel warmer by keeping in your body heat.
46
Your body is creating and killing about 2.4 million red blood cells per second.
17
If every muscle in your body could pull in one direction, you could lift nearly 25 tons.
22
The average person's skin weighs twice as much as their brain.
131