The human eye is an amazing mechanism, able to detect anywhere from a few photons to a few quadrillion, or switch focus from the screen in front of you to the distant horizon in a third of a second. How did these complex structures evolve? Joshua Harvey details the 500 million year story of the human eye.

Sometimes, against a uniform, bright background such as a clear sky or a blank computer screen, you might see things floating across your field of vision. What are these moving objects, and how are you seeing them? Michael Mauser explains the visual phenomenon that is floaters.

Whether we cry during a sad movie, while chopping onions, or completely involuntarily, our eyes are constantly producing tears. Alex Gendler tracks a particularly watery day in the life of Iris (the iris) as she cycles through basal, reflex and emotional tears.

An estimated 20 million cases of blindness worldwide are caused by cataracts, a curable condition affecting the lens that focuses images onto the eye’s retina. But how are cataracts formed, and how can we prevent them? Andrew Bastawrous gives the facts on cataracts.

There are three types of color receptors in your eye: red, green and blue. But how do we see the amazing kaleidoscope of other colors that make up our world? Colm Kelleher explains how humans can see everything from auburn to aquamarine.

Next Section »