The mission of our lab is to understand how cells obtain their shape, position organelles, move materials, and segregate chromosomes during cell division. Each of those functions relies on a specific architecture of the microtubule cytoskeleton. For instance, long and stable microtubules are required in an axon, whereas short and dynamic microtubules are arranged in a spindle to segregate chromosomes. How is this specific microtubule architecture established at the molecular level? We tackle this question using biophysical methods and X-ray crystallography in order to study the mechanism by which microtubules are organized at a structural level. In addition we combine biochemical, advanced light microscopy, and cell biological methods to examine the dynamic assembly of the microtubule cytoskeleton in its biological context.