Carrot is a root vegetable, native to Europe and Asia. Although we're most familiar with orange carrots, they do exist in purple, black and white varieties too. Carrots have been widely cultivated for hundreds of years, and are known to have been consumed in central Europe as long ago as 3000 BC.
Carrots are rich in carotenoids, pigments which give the vegetable its colour. The main carotenoid in carrots is beta-carotene, but carrots are also a good source of lutein and zeaxanthin, which are known to play a key role in good vision and eye health. Much of the beta-carotene in carrots will be converted to vitamin A by the body, which is also essential for eye health.
The story that carrots can help you see in the dark was actually started in World War II, as a British attempt to cover up the fact that their pilots were using radar! It's not entirely without foundation, however, as vitamin A is needed for the body to synthesise rhodopsin, which is responsible for low-light vision.
As well as carotenoids, carrots are also a good source of vitamins C and K, and of pantothenic acid, folic acid, manganese, potassium and copper.