Abstract
In the past 5-10 years, the power of the green fluorescent protein (GFP) and its numerous derivatives has been harnessed toward the development of genetically encoded fluorescent biosensors. These sensors are incorporated into cells or organisms as plasmid DNA, which leads the transcriptional and translational machinery of the cell to express a functional sensor. To date, over 100 different genetically encoded biosensors have been developed for targets as diverse as ions, molecules and enzymes. Such sensors are instrumental in providing a window into the real-time biochemistry of living cells and whole organisms, and are providing unprecedented insight into the inner workings of a cell.