Lens from a pair of glasses.
Lenses are an optical device that can be used to affect light beams through refraction. Changing the size and shape of the lens produce different results. Lenses have most commonly been used to correct vision, but are also used in a variety of other tasks, from viewing tiny microbes on the plate of a microscope to distant galaxies thousands of light years away in the night sky.
Lenses of all kinds can be found in many different stores.