The cilium (from Latin 'eyelash'; the plural is cilia) is an organelle found on eukaryotic cells in the shape of a slender protuberance that projects from the much larger cell body. There are two types of cilia: motile and non-motile cilia. Non-motile cilia are also called primary cilia which serve as sensory organelles. Most mammalian cell types possess a single non-motile, primary cilium, which functions as a cellular antenna. Exceptions include olfactory neurons which possess several non-motile cilia and cells of the transient embryonic node, which possess singular motile cilia known as nodal cilia, critical for the establishment of left to right body asymmetry.