Moss grows from tiny bits of plant called 'spores'. Spores are made by adult moss plants, but you can't see them with the naked eye. They are so tiny that you need a microscope to see them. The spores are spread by the wind or by animals, and if they land in a damp and shady place, they can start to grow into a new plant. Moss needs moisture to grow, so they like to grow in damp places, like the shady parts of your garden, or on the north side of a tree. When the spores land in just the right place, they will grow tiny green leaves, and send out roots to help it attach to the ground or tree. It will keep on growing, and new moss plants will form.