Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
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
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
The human body contains over a billion miles of DNA.
147
Your thumb is about the same size as your nose.
124
Dogs can be trained to identify the scent of lung cancer long before symptoms develop.
190
Enamel is hardest substance in the human body.
61