Scientists have created what they say is the world's first "living laser" capable of producing a laser beam, which could one day be used to activate drugs inside the human body.
Researchers at the Wellman Centre for Photomedicine at Massachusetts General Hospital in the US used a cell from a human kidney and genetically engineered it to produce light in the same way as a jellyfish and flooded it with blue light.
This caused a green laser to be beamed out of the other end that was visible to the human eye, the Daily Mail reported.
According to the researchers, in future, these "living lasers" could be produced inside live animals which would give unprecedented detail on scanners.
They could also have applications for computing and electronics and could one day allow doctors to treat cancers by lasering inside the body rather than from the outside, the researchers said.
Lasers have traditionally used two mirrors on either side of what is known as a gain medium, a material which amplifies light, such as a crystal.
An electrical discharge usually excites the molecules in the gain medium which fire out photons in random directions and are focused into a single point by the mirrors.
But, the new research, published in the journal Nature Phonetics, replaced the usual material with a human kidney cell that had been injected with green fluorescent protein (GFP), the material which makes jellyfish light up.
When the researchers fired a weak blue light through the GFP, they could see it begin to glow until a green laser came out the other end.
Lead researcher Dr Seok-Hyun Yun said their work was "the first report of a successful biological laser based on a single, living cell".
He said: "While the individual laser pulses last for only a few nanoseconds, they are bright enough to be readily detected and appear to carry very useful information that may give us new ways to analyse the properties of large numbers of cells almost instantaneously.
"The ability to generate laser light from a biocompatible source placed inside a patient could be useful for photodynamic therapies, in which drugs are activated by the application of light, or novel forms of imaging."