Neurofilaments are parts of the cytoskeletal structure of neurons and are abundantly found in axons. They are important for maintaining size and providing structural support for the neuron. There are currently five known neurofilament proteins that can co-assemble in different combinations. Originally, only three neurofilament proteins, named based on their size, were known: neurofilament light (NfL), medium (NfM) and high (NfH).