"Researchers at the University of Birmingham in the UK have created the world’s smallest atomic valentine, measuring just five nanometers by three-and-a-half nanometers. The previous record, set two years ago by the very same group, was eight nanometers.
That makes it smaller than the smallest wavelength of visible light, and thus invisible even under an optical microscope. But under an electron microscope, the researchers were able to image their heart made of palladium and somewhat more romantic gold atoms fitted to a carbon film. The heart shape was conjured by heating the nanoparticles in a certain way, altering their structures.”