Cacti are unique plants that thrive in dry environments, such as deserts. They have thick, fleshy stems that store water, allowing them to survive long periods without rain. Most cacti have spines instead of leaves, which help reduce water loss and protect them from animals that might want to eat them. There are many different types of cacti, ranging from small, round ones like the Mammillaria to tall, iconic varieties like the Saguaro. These plants are not only fascinating to look at but also play an important role in their ecosystems, providing shelter and food for various animals.