High-harmonic lightwaves tailored on demand by crystal symmetry. Light is made of an oscillating electric and magnetic field. In order to tune its properties, one would ultimately like to shape these fields directly – a specifically daunting challenge when the oscillation frequency is high. A team of physicists from Regensburg (Germany), Marburg (Germany), and Ann Arbor (USA) has now realized a way to directly tailor lightwaves emitted by accelerated electrons inside a solid, with the aid of the crystal’s symmetry. The results of this breakthrough will be reported in the upcoming issue of Nature Photonics. For several years, physicists have been able to routinely produce extremely short flashes of light in the hard ultraviolet or even soft x-ray spectral region. For this purpose, a method called high-harmonic generation is employed, where a strong near-infrared laser rips electrons from an atomic gas and slams them back into the nuclei to emit ultraviolet radiation upon recollision.