A still life is a painting or drawing that depicts inanimate objects, typically commonplace items such as flowers, fruits, and household items. The term can also refer to a work of art consisting solely of such objects. The purpose of still life paintings and drawings was historically primarily functional. Early still-life works were often produced in order to be used as teaching aids for artists who wished to learn how to skillfully represent various objects. With the development of the decorative arts and art academies in the 17th century, still lifes became one of the genres regularly taught to aspiring artists. Still life works are often included in museum collections due primarily to their aesthetic value, but sometimes also for historical reasons (e.g. as with paintings of particular foods which are no longer available). Paintings depicting food and drink in still life were particularly popular in 17th-century Netherlands. The genre began to declined in popularity in the 18th century, but experienced something of a revival in the 19th century. The works of Paul Cézanne, an important proto-Cubist painter, frequently included still life elements. Vincent van Gogh also painted many still life works during his post-Impressionist period. Still lifes often consist of ordinary objects which may be either natural (such as flowers, fruits, dead animals, plants, rocks, or shells) or man-made (such as books, vases, jewelry, coins, pipes, and so on).