Inside ALS: The neurons behind the disease Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that mainly affects the nerve cells (neurons), which control muscle movement. As the motor neurons degenerate, they stop sending signals to the muscles, causing progressive muscle weakness and — ultimately — death. This animation focuses on the mechanisms within the motor neurons that cause them to degenerate. By understanding these mechanisms, researchers hope to one day find a cure for ALS. To learn more about ALS, check out the Primer: https://www.nature.com/articles/nrdp201771 and the PrimeView: https://www.nature.com/articles/nrdp201772 Nature Research has full responsibility for all editorial content, including Nature Video content. This content is editorially independent of sponsors.