Laser physicists have found a way to make atomic-force microscope probes 20 times more sensitive and capable of detecting forces as small as the weight of an individual virus. The technique hinges on using laser beams to cool a nanowire probe to -265 degrees Celsius. "The level of sensitivity achieved after cooling is accurate enough for us to sense the weight of a large virus that is 100 billion times lighter than a mosquito," said one researcher.