Fungi (that's what we call more than one fungus) are really tiny living organisms. They grow in lots of places such as in dirt and on food. They can also grow on the skin, in the hair and even in the nails of almost all living creatures. Sounds a bit yucky doesn't it? Mushrooms and toadstools are fungi too, but they are very different to the ones that grow on the skin. Fungi can come in lots of different shapes and colors - have you seen the green or brown fungi that grow on very old bread?