Ema are small wooden plaques on which Shinto worshipers write their prayers or wishes. The Ema are then hung at the shrine, where the kami (spirits or gods) are believed to receive them. They bear various images, often of animals or other Shinto images, and many have the word gan'i, meaning "wish," written on the side. In ancient times, people would give horses to shrines as a gesture of goodwill, over time this was transferred to a wooden plaque with an image of a horse, and later still to the various wooden plaques sold today for the same purpose.
