Crassula tillaea is a succulent plant known by its common names mossy stonecrop and moss pygmyweed. It is a small fleshy plant growing only a few centimeters in height. It is green when new and gradually turns orange and then deep red when mature. It has tiny triangular pointed leaves only a few millimeters long. A tiny flower or pair of flowers grows between each oppositely-arranged pair of leaves; the flowers are about two millimeters in length and width. The fruit is a minute follicle containing one or two seeds. This plant is native to Eurasia, particularly the Mediterranean Basin, but is known in other regions as an introduced species.