Fig. 1. Structures of centrioles and cilia. (A) The structure of the canonical motile 9+2 axoneme and its most common variation, the immotile 9+0 axoneme. (B) Schematic of a transverse section through the immature and mature centrioles. (C) Schematic of a longitudinal view of the mature centriole, showing the appendages, and a basal body with accessory structures.