Unlike most animal organisms which exhibit some type of body symmetry, such as radial, bilateral, or spherical symmetry, most sponges are asymmetric, exhibiting no type of symmetry. There are a few species, however, that are radially symmetrical. Of all the animal phyla, Porifera are the simplest in form and most closely related to organisms from the kingdom Protista. While sponges are multicellular and their cells perform different functions, they do not form true tissues or organs.