Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
The human brain doesn't stop developing until about 25 years old.
102
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
The average person's skin weighs twice as much as their brain.
131
If you are cold you are more likely to be hungry because you use energy to keep warm.
143
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