The biggest genus in the Cactaceae family (between 200 and 400 species depending on recent fashion wave). Can be met with in many countries, from Columbia to USA. They have “nipples” or mammillas instead of ribs and their flowers appear in the form of a circle around the apex and not in the apex itself. This is the main difference between them and Escobaria and Coryphantha. They vary in size very much as well as in shape, flower size and colour, spine form etc. Some of them are extremely easy in cultivation (like M. elongata), some are extremely tough (like the big-flowers miniatures of the M. saboae type). In any case open substrate is required and a lot of sun and heat, watering should be generous but infrequent. So called “white Mammillarias” (of white spination like M. candida) need alkaline soil, with limestone chippings or lime added. In winter the average temperature of 6–12°C is best, light would be appreciated but not absolutely necessary.