Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Your heart will pump about 212 million liters in its lifetime.
26
The average sperm cell swims at 8 inches per hour.
76
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
The human brain uses approximately as much energy as a 10 watt light bulb.
120
One human hair can support 3 ounces.
191
Enamel is hardest substance in the human body.
61