• The average blink lasts for about 1/10th of a second.

• Newborns don't produce tears. They make crying sounds, but the tears don't start flowing until they are about 4-13 weeks old.

• Out of all the muscles in your body, the muscles that control your eyes are the most active.

• Some people are born with two differently colored eyes. This condition is heterochromia.

• Even if no one in the past few generations of your family had blue or green eyes, these recessive traits can still appear in later generations.

• Seeing is such a big part of everyday life that it requires about half of the brain to get involved.