A fly only has 2 eyes

Most people think flies have hundreds of eyes but a fly only has two eyes.

A fly has one on each side of its head. Each eye is a compound eye meaning the same facet is repeated 800 times (for fruit flies). 

Each facet is called an ommatidia or simple eye. Each ommatidia is composed of a set of photoreceptor neurons that detects light.

author: Larry Lim