Researchers at the Jožef Stefan Institute have succeeded in making a very important breakthrough - for the first time they were able to implant a laser into a single human cell. Furthermore, they have demonstrated that the fat cells in our body already contain lasers, which need only to be activated. In both cases the lasers are in the form of small solid spheres or lipid droplets. Deformation of the droplets enables accurate measurements of the forces inside the cells. The emission of each laser within a cell can also be used as a barcode with enough unique combinations to tag all the cells in the human body. This discovery was published in the Nature Photonics paper Intracellular microlasers. The authors are Dr Matjaž Humar from the Condensed Matter Physics department of the JSI, who is currently on a postdoc at Harvard Medical School, USA, and Seok-Hyun Yun - video.