A magneto-optical trap. We just got it back up and running again after many days of realigning things (which is quite a pain, but it builds character ). The image is taken from a TV screen since the collection of atoms shown (the bright, white dot in the center) scatters light very dimly in the near-infrared, so our eyes can't see them, but security cameras can. The collection of atoms in the center is just above absolute zero (-273.15°C) by millionths of a degree. I don't remember off hand what the number of atoms is in the trap, but I'm assuming it's fairly large (~10⁶?).