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
Yawns are more contagious among people with closer relationships.
163
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Every year your body replaces 98% of your atoms.
119
The human brain uses approximately as much energy as a 10 watt light bulb.
120
Enamel is hardest substance in the human body.
61
An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73