Genetically encoded fluorescent biosensors are fluorescent proteins attached to an additional protein sequence that make it sensitive to small biomolecules or other physiological intracellular processes. Fluorescent biosensors are introduced into cells, tissues or organisms to allow for detection by fluorescence microscopy as a difference in FRET efficiency, translocation of the fluorescent protein or modulation of the fluorescent properties of a single fluorescent protein. Many biosensors allow for long-term imaging and can be designed to specifically target cellular compartments or organelles. Another advantage of biosensors is that they permit investigation of a signaling pathway or measurement of a biomolecule while largely preserving spatial and temporal cellular processes.