Lab mouse. Coloured scanning electron micrograph (SEM) of the head of a BALB/c mouse. One of its eyes and large ears can be seen, along with its long whiskers protruding from its nose. The BALB/c mouse is an albino strain of the common house mouse (Mus musculus). First bred in New York, USA, in 1920, they are now one of the most common strains used for animal testing. Magnification: x4 when printed 10 centimetres wide.