In this work, we aim at studying experimentally the bubble formation process in a microfluidic flow-focusing device using both the -PIV technique and a high speed digital camera, in particular investigate the gas bubble breakup process and the various parameters affecting the bubble formation, such as flow rates of both phases and continuous phase viscosity. The breakup rate and the collapse time of the gaseous thread were described as a function of the ratio of the gas/liquid flowrates and the Reynolds number