Nymphaeaceae is a family of flowering plants. Members of this family are commonly called water lilies and live in freshwater areas in temperate and tropical climates around the world. There are about 70 species of water lilies around the world. Water lilies are divided into two main categories: hardy and tropical. Hardy water lilies bloom only during the day, but tropical water lilies can bloom either day or night, and are the only group to contain blue-flowered plants. Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on the water surface.