One of the few quite cosmopolitan genera in Cactaceae, it grows in Mexico, Central America and South America. They are globular, medium in size, and when adult they produce a kind of a cap (called cephalium) on the apex that tiny flowers (and very decorative fruits) grow from. They need open potting mix, in summer should be watered frequently (constantly slightly humid soil), kept in a hot greenhouse if possible. In winter they must be provided with 12°C minimum, light is less important. You can keep them on a windowsill during winter. For the cephalium (and flowers) one has to wait more or less 10 years from seed.