The name Mammillaria comes from the Latine for "nipple", because the areolas (structures carrying the spines) are carried by nipple like structures instead of being organized in ribs like many other cacti. Native to Mexico, Nipple Cacti are one of the largest group in the cactus family. Pretty Nipple Cactus intially has a solitary round stem, up to 6 inches tall and 3 inches wide. Later they form clusters by abundant dichotomous branching. Each nipple has white wool and bristles on it. Flower are purplish red to deep pink, to 10 mm long and in diameter.