Ground-based optical telescopes suffer from the atmosphere through which light from distant stars has to travel before actually reaching them. During this passage, the originally flat fronts of the light waves become distorted, and the images generated by the telescopes become unsharp and fluctuate. Adaptive optics can measure and compensate such effects by deploying so-called wavefront sensors and deformable mirros, allowing to re-establish sharp images in the focal plane. The ultimate amount of detail contained in the images is then only limited by the size of the telscope, which, with the advent of ESO’s ELT, will soon be 39m in diameter. The video shows how we can measure the shape of an incoming wave front, and subsequently (re-)flatten it, so that images of unprecedented detail can be obtained.