This one seems right out of the latest X-Men film.

Scientists have merged light-emitting proteins from jellyfish with a single human cell to create a unique first: a living, biological laser, according to a report published in the journal Nature Photonics.

"This is the first time that we have used biological materials to build a laser and generate light from something that is living," said Seok-Hyun Yun, an optical physicist at Harvard Medical School and Massachusetts General Hospital in Boston, who created the "living laser" with his colleague Malte Gather.

Lasers require two elements: a material that amplifies light, called a "gain medium," and an arrangement of mirrors to concentrate light waves into a beam. Gain mediums have traditionally been crystals, semiconductors or gases. Yun and Gather turned instead to green fluorescent protein (GFP) -- the substance that makes jellyfish bioluminescent.

The team engineered human embryonic kidney cells to produce GFP, then placed a single cell between two mirrors to make an optical cavity just 20 micrometres across. When they fed the cell pulses of blue light, it emitted a directional laser beam visible with the naked eye -- and the cell itself wasn't harmed in the least, reported Nature.com.

The laser beam is tiny and weak compared with traditional lasers, the researchers said, but still an order of magnitude brighter than natural jellyfish fluorescence, with a "beautiful green" color.

Yun and Gather have big plans for living lasers. They suggest biologists could use them to study a specific cell in the body, turning it into a living laser to examine the cell's structure. Or doctors could do the same, turning on a laser within a person's body to treat a disease attacking cells.

Yun pictures a future where cells could even "self lase" from within the body's tissue.

"I have been working on cells and lasers for 40 years, and I don't think I would have thought of this," Michael Berns, a biomedical engineer at the University of California, Irvine, told Nature.com.

Read more about living lasers at Nature.com.