Particle Image Velocimetry (PIV) is a robust technique for measuring fluid velocity. The method is an optical, non-intrusive technique measuring the movement of smalltracer particles by means of a camera and pulsed laser light. When applying the PIV technique to microfluidic devices, a microscope is a natural and practical workbench. The technique is a strong experimental tool that rapidly and intuitively provides measurement results comparable to CFD simulation results. Hence, the technique is of great benefit in rapidly developing new microfluidic devices.