The pear is any of several tree and shrub species of genus Pyrus, in the family Rosaceae. The pear is native to coastal and mildly temperate regions of the Old World, from western Europe and north Africa east right across Asia. It is a medium-sized tree, reaching 10–17 metres (33–56 ft) tall, often with a tall, narrow crown; a few species are shrubby. Pears and apples cannot always be distinguished by the form of the fruit; some pears look very much like some apples, e.g. the nashi pear. One major difference is that the flesh of pear fruit contains stone cells (also called "grit"). Pear cultivation in cool temperate climates extends to the remotest antiquity, and there is evidence of its use as a food since prehistoric times.