The image above was created using transmission electron microscopy (TEM), using a flux of electrons with 10,000 electron volts of power to produce an image of gold nanoparticles magnified 30,000 times. The gold nanoparticles represented in the picture are small spheres of gold with a diameter of between 18 and 22 billionth of a metre. Gold nanoparticles have the tendency to aggregate to form metallic gold, this is prevented by covering the surface of the particles with small, charged molecules that repel the other particles. These small molecules can be used to add different properties to the nanoparticles: tumour tracking, fluorescence, drug release etc.