These are organisms that include yeasts and molds as well as mushrooms. Like plants, fungi cells have a rigid wall around them. However, there are differences between the cell wall of a plant and that of a fungus. The cell wall of plants is mostly made of cellulose, whereas the cell wall of fungi is mostly made of chitin and glucans. Glucans are also found in the cell wall of plants, but they typically make up at least half of the cell wall of fungi. This makes the fungal cell wall very sturdy and resistant. Chitin is a strong, durable chemical which protects the fungal cells from harm and provides them support. Interestingly, chitins are also found in the exoskeleton or external hard skeleton of insects and crabs. Like plants, fungi often grow in soil and, in the case of mushrooms, form visible fruiting bodies, which sometimes resemble plants such as mosses.