Cornea

Light reflected off objects- the cornea bends the light rays that pass through the pupil

Free if you are born with it

$11,000

Corneal tissue- a highly organized group of cells and proteins with five layers (the epithelium, Bowman's layer, the stroma, Descemet's membrane, and the endothelium)

There are many theories concerning the "invention" of the cornea (and the human body in general), including religious (ex: as an element of Creationism) and scientific theories (ex: as a subset of the Big Bang theory). Regarding man-made false corneas and cornea-enhancers (contact lenses), Leonardo da Vinci produced sketches in 1508 which suggested that the optics of the human eye could be altered by putting the cornea in contact with water. Many believe that his ideas led to the development of contact lenses more than 350 years later. English astronomer Sir John Hershel proposed making a mold for the human eye in 1827, and some say that German glassblower F.A. Muller created the first contact lens (made of glass) in 1887. Other says that Swiss physician Adolf E. Fick and Paris optician Edouard Kalt created the first glass contact lens in 1888.