Mammillaria is one of the largest and most diverse cactus genera, with species ranging from tiny solitary plants to clustering forms. Instead of traditional ribs, their bodies are covered with organised tubercles, each bearing an areole and spines. Many Mammillaria species produce rings or crowns of small flowers around the top of the plant, followed by colourful fruits. Their variety of shapes, spine patterns, sizes and flowering habits makes Mammillaria a versatile group for both beginners and experienced cactus collectors.