The LaVision Flow Master 2-D µPIV System is designed to measure velocity fields of particle seeded flows with micron scale spatial resolution using particle image velocimetry (PIV) techniques. The light source is a double pulsed Nd:YAG laser that is focused by an epifluorescence microscope with a high numerical aperture on a microfluidic device. The microscope lens collects the fluorescence signal emitted from the particles at a longer wavelength than the illuminating light. This signal is separated from the laser light by a filter cube and is recorded by a double-frame CCD camera (Imager Pro X 2M). The double frame images are evaluated with conventional PIV algorithms.