A human cell has been engineered to form the light source of a tiny laser — creating the first laser to use biological material to generate light.

Malte Gather and Seok-Hyun Yun at Harvard Medical School in Boston, Massachusetts, engineered human cells to express an enhanced version of green fluorescent protein. They then sandwiched a suspension of the cells between two tiny, closely spaced mirrors to concentrate and align the light waves from the cells into a tight beam. By pulsing individual cells with blue light, the researchers excited the fluorescent proteins, causing them to emit light (two different lasing levels, pictured). The result was a bright directional beam of green laser light visible to the naked eye.

Nature Photonics doi:10.1038/nphoton.2011.99 (2011)