The Microscopy and Molecular Imaging Working Group specializes in the development of novel imaging instruments and molecular reagents for the study of cells, tissues, and living organisms. Stanford researchers have developed microscope instruments combining molecular trapping with high sensitivity fluorescence detection to allow precision manipulation and measurement of single molecules. Custom-designed, micro-optical probes allow in-vivo imaging of neurons and neuronal circuits, providing insight into the molecular and cellular basis of learning and memory. Two-photon, confocal, and multi-aperture microscopes permit measurement of the three dimensional internal structure of cells in vitro, while novel endoscopic microscope instruments provide images of cells in live animals, enabling in vivo pathology. Researchers at Stanford also have developed genetically engineered bacteria which produce bioluminescent molecules when specific genes are activated, providing a method for imaging precisely the location of points of infection and a noninvasive method for monitoring the effectiveness of antibiotics in real time.