What's the News: Scientists have developed the first biological laser, made from a single living cell. This "living laser," described in a new study in Nature Photonics, could one day lead to better medical imaging and light-based treatments for cancer or other diseases. How the Heck:

Lasers typically have several parts: a material called a gain medium, which amplifies light; an energy source to "pump" the gain medium, exciting its atoms and enabling it to emit more powerful light; and mirrors, which direct the light into a coherent beam.

To start, the researchers modified cells derived from a human kidney to manufacture green fluorescent protein, or GFP, a molecule that glows green when exposed to blue light. This glowing cell served as the laser's gain medium.

The researchers then nestled the cell between two mirrors, which were close enough together to form a cell-sized cavity, and shone pulses of blue light---the energy source---onto the cell through a microscope.

Blue light would simply make the cell glow, under normal conditions. In this mirrored cavity, however, the photons bounced around, exciting more GFP molecules. This meant the cell could amplify the light---eventually emitting a green laser beam more powerful than the blue light that pumped it. The cell was able to emit a few hundred laser pulses over several minutes before its GFP wore out.