Part fungus and part alga, lichens defy simple classification, and are perhaps best thought of as dual citizens of two kingdoms of life. The fungal portion of a lichen transports water and soil nutrients, while the algal portion produces energy through photosynthesis.* Standing a mere inch tall, the common blue-gray Pixie Cup Lichen (Cladonia sp.) grows among mosses on the forest floor, on dry, exposed soil in sunny spots, on bricks or bare rock, or between planks of weathered wooden decking.
*This is certainly an oversimplification, but as an amateur lichenologist, I dare not get more specific. If you know more about the fascinating lives of lichens, I encourage you to leave a comment below.