The world's smallest laser, contained in a silica sphere just 44 nanometres across, has been unveiled. At about 10 times smaller than the wavelength of light, however, this is no ordinary laser, it is the first ever 'spaser'. Whereas a laser amplifies light, using a mirrored cavity to intensify it, a spaser amplifies surface plasmons — tiny oscillations in the density of free electrons on the surface of metals, which, in turn, produce light waves. The spaser could be used as a light source for scanning near-field optical microscopes, which can resolve details beyond the reach of standard light microscopy,...