A beam of electrons was first observed to be accelerated with a ‘gradient’ – or energy transfer rate – of 300 MV/m, which is very high for present-day accelerators, in a device rather like a microchip. This was made of silica glass and powered by a commercial laser beam, at the SLAC laboratory in the USA. It opens the way to build a particle accelerator “on a chip” much more cheaply than conventional ones. However, few studies have been done of the all-important quality of the particle beam that can be obtained from such a ‘micro accelerator’.