Yawns are more contagious among people with closer relationships.
163
The average sperm cell swims at 8 inches per hour.
76
It takes about 20 seconds for a red blood cell to circle the whole body.
102
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
The human brain doesn't stop developing until about 25 years old.
102
Enamel is hardest substance in the human body.
61