The Fabaceae is the family that used to be called the Leguminosae, and is the bean, pea or legume family. The name comes from the genus Faba, which is now part of Vicia. It is the third largest family after orchids and sunflowers, and contains over 700 genera and almost 20,000 species. It is divided into three sub-families which are treated as full families  by  some,  Mimosoideae, Caesalpinoideae, and Faboideae. Leaves are typically alternate and pinnately compound, although many are trifoliate or palmately compound. Flowers are made up of five usually fused sepals and five free petals. Most commonly the fruit is a legume which is a pod that opens along a lengthwise seam. The Fabaceae is one of the most economically important plant families in the world, and has long been closely associated with the development of human societies.