Mammillaria is a genus of cacti native to the Americas, particularly found in Mexico and the southwestern United States. These cacti are characterized by their small, rounded shape and distinctive tubercles, which are small, nipple-like projections on their surface. They often produce colorful flowers that bloom in a ring around the top of the plant, adding to their ornamental appeal. There are over 200 species of Mammillaria, making it one of the largest genera of cacti. They thrive in arid environments and are well-adapted to survive with minimal water. Many species are popular among collectors and gardeners due to their unique appearance and relatively easy care requirements.