How are lichens different from other groups of organisms?

Lichens are an association between one or two types of fungi and algae or cyanobacteria (blue-green algae), resulting in a different form than symbionts. Although lichens appear to be singular plants, under the microscope, their associations are made up of millions of algal cells (phycobionts) woven into a matrix of fungal filaments (mycobionts). Although lichens have long been thought to be made up of one type of fungus and one phycobion, research shows that many of them also have specific Basidiomycete yeast in their bark.