It's so well constructed. You've got the iris, the cornea, the pupil, and the sclera, are all working together to allow us to see. The eye muscles have to be fast. Just to track an object involves ...

That coloured circle is called the iris and the black spot in the middle is the pupil. This is the part of the eye that lets the light in. Lights out please! When it’s dark, muscles in the iris ...

Eye color depends on the iris, the colored part of the eye. It's a structure that contains muscle and other kinds of cells. You can see the iris in action when it squeezes or relaxes to let in ...