This vibrant pattern shows lead-sulfide nanocrystals evaporated on top of silicon. The circular islands represent larger 3-D "supercrystals". The colors are natural, unretouched by photo-editing tools. Learning how nanoparticles behave could help scientists tailor them for use in solar cells, batteries and other energy devices. Lead sulfide refers to compounds containing lead and sulfur. Silicon is a chemical element with symbol Si and atomic number 14. It is a tetravalent metalloid and the 8th most common element in the universe by mass, but very rarely occurs as the pure free element in nature. A nanocrystal is a material particle having at least one dimension smaller than 100 nanometers (a nanoparticle) and composed of atoms in either a single-crystalline or poly-crystalline arrangement. Nanotechnology (nanotech) is the manipulation of matter on an atomic, molecular, and supramolecular scale.