Lichens are just one of the miracles of nature that I find fascinating. At first, you might think lichens are plants. They're not. Maybe a fungus? Well, could be, but that's only partially correct. Lichens are actually composite and symbiotic organisms made up from members of as many as three kingdoms. Here's a bit more, from one of my favorite lichen sites:
"The dominant partner is a fungus. Fungi are incapable of making their own food. They usually provide for themselves as parasites or decomposers... These lichen fungi cultivate partners that manufacture food by photosynthesis. Sometimes the partners are algae (kingdom Protista), other times cyanobacteria (kingdom Monera), formerly called blue-green algae. Some enterprising fungi exploit both at once.
It is estimated that lichens are the dominant vegetation on 8% of the earth's terrestrial surface."