Enamel is hardest substance in the human body.
61
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
It would take about 1,200,000 mosquitoes to fully drain the average human body of blood.
217
Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
197
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
Yawns are more contagious among people with closer relationships.
163
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118