1) Microtubules grow by the addition of tubulin dimers to the plus end, with polymerization favored at this end. The plus end carries a GTP cap that stabilizes the microtubule. 2) Microtubules undergo treadmilling as the GTP cap moves down the length of the microtubule until reaching the minus end, where GTP is hydrolyzed. 3) Dynamic instability occurs when a microtubule switches between growth and shrinkage, providing a source of tubulin for other microtubules. Growing microtubules are favored when GTP-tubulin concentrations are high.