Nestled amidst the cytoplasm is the cytoskeleton: tubular filaments of protein termed microtubules, which provide cellular scaffolding and form the internal structure of cell tails – both cilia and flagella. Cytoskeletal elements extensively and intimately interact with the cell membrane.
Tubulins are the family of proteins that comprise microtubules. Tubulins are the guides by which cells know their internal organization. The asymmetric configuration of cells, whether prokaryote or eukaryote, and even left-right organ placement in multicellular organisms, owes to tubulins driving patterning during development. How tubulins know and coherently provide their orientation guidance is a mystery.