Mammillaria is a diverse genus of cacti known for its small, globular to cylindrical-shaped plants. They are characterized by their distinctive tubercles, which are small, nipple-like projections on the surface of the cactus. Mammillaria cacti often produce colorful flowers that emerge from the top or sides of the plant. They are popular in the world of cacti and succulent collectors due to their varied and intriguing appearances. These cacti are native to various regions of the Americas, particularly Mexico.