Microtubules are involved in many activities within the cell that require highly dynamic activity. For examples, microtubules can grow and shrink as they explore the cell, and the entire microtubule cytoskeleton is restructured as cells prepare for division. Interfering with microtubule dynamics can have serious consequences for the health of the cell, especially in cells that are rapidly dividing. The result of disrupting the normal dynamics is generally an interruption of the cell cycle and consequent induction of apoptosis. This behavior has been exploited with a number of anti-cancer drugs that target tubulin, the main protein in microtubules. Drugs are currently in use that either stabilize or destabilize microtubules. Among the most widely used is Taxol, one of the microtubule stabilizing drugs. Because Taxol produces a range of serious side effects and a substantial fraction of patients treated with Taxol eventually develop resistance to the drug, there is an active search for other drugs that might be more selective and less prone to resistance.