Have you ever noticed that the color of some lichens is a more intense green after they get wet? There’s a very good explanation for this phenomenon. Lichens are made up of an alga or cyanobacterium and a fungus. The alga or cyanobacterium makes the food, and the fungus absorbs the water. A typical lichen has a three-layered structure. A middle layer containing algal cells entwined in threadlike fungus fibers called hyphae is sandwiched between two layers of fungal tissue. Lichens that turn bright green after it rains contain green algae which contains chlorophyll, a green pigment. When it rains, the fungus (which surrounds the algae) soaks up water like a sponge, causing the fungus to become more transparent, which allows the green pigment of the algae to be seen more clearly.