Fungi are living organisms that are more closely related to animals than to plants. Like animals, fungi do not have chlorophyll and thus cannot produce their own food. Instead, they digest food outside their bodies by releasing enzymes into the surrounding environment and breaking down organic matter into a form the fungus can absorb. As such, fungi provide the important function of recycling dead organic matter into useful nutrients. The largest part of a fungus is often invisible: soft, thread-like hyphae spread throughout the host organism, such as rotting wood, or in the ground, making up the structure known as the mycelium. The mycelium produces a carpophore, also called a fruiting body, which emerges into the air to release spores. It is the fruiting body that is most readily seen, and different species produce different types: from the shelf fungi which grows on trees to the familiar mushroom growing in a quiet wood, to puffballs and jelly-like substances growing on rotting logs.