"The aim of this proposal is to make a laser composed entirely of living cells and materials derived from living organisms. The central part of the laser will consist of human embryonic kidney cells engineered to produce enhanced green fluorescent protein. The cells will provide gain for the laser. The resonant cavity will be made in three different ways, either using butterfly wings as highly reflective mirrors or using a droplet of water to circulate light or by highly scattering particles that will induce random lasing. This project goes well beyond bio-inspired technologies, which are based on principles from nature, but use artificial materials. A step forward is to use biocompatible materials or materials derived from living organisms. By using live cells this proposal goes even further. The advantage of this concept is self-assembly, self-healing, self-reproduction, scalability, self-reproduction, evolvability and adaptability of such living laser. The use of the living laser spans a variety of possible applications. The lasing spectrum emitted by the living laser has a unique pattern, which can be used to study the processes in the cell as well as for sensing external substances affecting the cell. We also suggest possible medical applications. Doctors today shine lasers into the body to gather images or to treat disease. The living lasers could instead generate or amplify the light inside the body, so it could penetrate the relevant tissues more deeply. Finally, future optical circuits could be made entirely of living tissues enabling their integration into living organisms."