People seem to be asking a lot of questions like "aren't atoms are too small to see and move?" and "why can't we see the background?" I'm going to try and explain. What you are looking at is not a photograph of actual atoms, atoms don't look like anything because they are too small for light to be used to see them. This image was created using a machine called a "scanning tunneling microscope." This machine works by using a microscopic probe (picture above) generating an electric charge to essentially 'feel' the size and position of the atoms, or at least their charge. Since humans see with light instead of electric charges, the microscope must then use this data to generate a computer image representation of the charges it feels letting us see what it sees (this is what you see in the film). This is why they are silver balls, because we can't see the atoms but instead are seeing a representation of the field created by the electrons, and also why atoms out of the probes range don't show up.