Intense light bent out of shape - ultrafast lenses made from gas Researchers from the MPIK in Heidelberg used an atomic gas as a time-dependent lens to shape and spectrally manipulate intense high-frequency laser pulses. This gas-based optical element could pave the way toward better XUV- and x-ray pulse control for applications such as chemical reaction steering, quantum computing, and advanced spectroscopy methods for fundamental science. ● High-frequency (XUV) light offers unique insight into fundamental atomic processes, but control of light on microscopic scales in space and time remains a challenge ● Novel beam shaping technique: researchers demonstrate manipulation of XUV pulses spatially and spectrally ● Gas as a laser-controlled optical element: non-linear interactions in helium gas create an intensity-dependent refractive index near resonance – the gas acts like a lens or prism that can be turned on and off extremely fast. Controlling the Light The first known man-made lenses to manipulate light dates back to 700 BC: a nearly four-centimetre-wide rock crystal piece, manufactured around that time, was found in Nimrod, Iraq. And while the intended original function of this lens is not entirely clear today, it still shows that as early as this, humans were aware of the light-focusing properties of materials. An important application of this knowledge was the invention of microscopes, more than two millennia later, that utilised the optical properties of focusing glass lenses to explore the previously unknown microscopic world. With the invention of lasers and subsequently short, intense laser pulses, scientists are now able to produce high-energy light at extreme intensities for very short periods of time, enabling more precise material-processing options, but also opening further insights into microscopic processes. The shorter the wavelength of the light used, the shorter the pulses can be – and the more precisely we can peer into