Gold nanoparticles, in fact, are even more surprising when you observe them through a microscope. Regular microscopes use visible light and optical lenses to enlarge microscopic objects. Gold nanoparticles, however, are so small that a typical microscope is unable to resolve them. Even smaller than the wavelength of visible light, these particles can only be seen with an electron microscope: a much more advanced technology that uses an electron beam capable of revealing objects as small as atoms.

When visualized with electron microscopy, gold nanoparticles disclose another secret. Their shapes are surprisingly regular, with uniform size and perfectly geometrical appearance. They spontaneously arrange themselves in beautiful regular patterns, as if they were tiles in an ancient mosaic.