I'm guessing there are at least two layers of glass between that atom and the sensor. Not really specific to this (excellent) picture, but I imagine that avoid

I'm guessing there are at least two layers of glass between that atom and the sensor. Not really specific to this (excellent) picture, but I imagine that avoiding distortion due to the glass or smudges on the glass must be a huge part of high magnification photography. The whole light from a single atom part just makes it more amazing how clean and clear that window is...