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 person's skin weighs twice as much as their brain.
131
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
Your thumb is about the same size as your nose.
124
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