Colloidal gold is nanoparticles of pure gold suspended in pure water. The gold nanoparticles in TM3 Liquid Gold are a few nanometers in diameter (a nanometer is a billionth of meter). These particles are so small they can only be seen by the most powerful electron microscopes available today. An atom of gold is about 0.288 nanometers in diameter, so the gold nanoparticles in TM3 Liquid Gold are only about eleven times the diameter of a single gold atom. These particles stay suspended in pure deionized water and do not fall to the bottom. It is these suspended particles that make TM3 Liquid Gold a true colloid.