Since the earliest microscopes, scientists have been on a quest to build instruments with finer and finer resolution to image a cell’s proteins – the tiny machines that keep cells, and us, running. But to succeed, they need to overcome the diffraction limit, a fundamental property of light that long prevented optical microscopes from bringing into focus anything smaller than half the wavelength of visible light (around 200 nanometers or billionths of a meter) – far too big to explore many of the inner-workings of a cell.
