Light-induced structural transformations in a single gallium   nanoparticulate
  In a single gallium nanoparticulate, self-assembled (from an atomic beam) in a nano-aperture at the tip of a tapered optical fiber, we have observed evidence for a sequence of reversible light-induced transformations between five different structural phases (gamma - epsilon - delta - beta - liquid), stimulated by optical excitation at nanowatt power levels. 
B. F. Soares, K. F. MacDonald, V. A. Fedotov, and N. I. Zheludev