Mycorrhiza are a symbiosis between plant and fungi. To find each other fungi and plants release volatiles. Once they start living in a symbiosis they can form giant networks below the ground. While the plant supplies the fungi with carbon hydrates, it receives mineral nutrients and water in exchange. But there is more to this relationship. In forests these giant mycorrhizal networks connect trees to fungi and in this way to each other. This network is used to constantly exchange information. This information can even alter the plants headspace scent, for example as a reaction to stress. Using these mycorrhizal networks larger trees can also supply saplings growing in their shade with sugars, so they can survive till the larger trees die and sunlight eventually reaches them.