Book excerpt: As an intricate association between a fungus and one or more green algae or cyanobacteria, lichens are one of the most successful examples of symbiosis. These fascinating organisms survive extreme desiccation and temperatures. They are adapted to a great variety of habitats, from coastal fog zones of deserts to intertidal zones, from plant leaves in tropical rain forests to the glacial moraines of the Himalayas, and they are dominant components of communities in circumpolar ecosystems. Possibly, because of their tendency to grow in nutrient-poor habitats, lichens are extremely efficient accumulators of atmospherically deposited pollutants, and are therefore widely used to monitor environmental pollution. The wide range of secondary products only found in lichens show pharmaceutically interesting fungicidal, antibacterial and antiviral properties. Lichens are extremely difficult to culture, grow very slowly, and their secondary metabolites very often complicate the analyses of other compounds. As a result, they require special techniques. This manual provides well-tested protocols, including tissue culture protocols and methods for studying lichen ultrastructure, (eco)physiology, primary and secondary compounds, and nucleic acids. Protocols for using lichens to monitor environmental pollution and to document lichen biodiversity are also provided. Special terms used in lichenology are explained in a glossary.