LIDAR is the first generation of laser remote sensing deve loped for detection of gas molecule in atmosphere. LIDAR is the abbreviated word for laser radar (laser light detection and ranging). It combines advantages of lasers ability to detect atoms and molecules and radars ability for remote sensing. The advance of technologies: tunable solid state laser (Ti-sapphire, O PO etc), optical fiber, photonics imaging technique and last but not least compu tational techniques, have promoted the development of new types of laser remote sensors capable of detecting toxic and radioactive chemicals and metals not in g as form and not exposed in air but under ground water and subsurface soil. The h igh power laser is used to vaporize the target material and generate plasma. Opt ical fiber is often used to delivery the laser beam and to collect the emission for imaging. The combination of spectroscopy with advanced photonics imaging te chniques can study both the chemical components of sample in-situ under ambient conditions and spatial distribution of different chemicals in remote operation without requiring sample preparation or extensive sample handing. These new deve lopments have greatly enlarged the horizon of traditional capability of remote s ensing.