This thesis presents the experimental and computational study of hydrogel microgels using flow-focusing devices. The microfluidic devices were fabricated to generate microgels from two immiscible phases of fluids. Conventional replica molding and photolithography methods were used to fabricate a rectangular channel microfluidic device. Using the flow-focusing microfluidic devices, effects of various parameters on hydrogel pre-polymer droplet generation were investigated experimentally and computationally. First, three-dimensional (3D) computational simulations were conducted to study the physics of hydrogel pre-polymer droplet formation mechanism in three different regimes:​ squeezing, dripping, and jetting regime. Subsequently, effects of viscous, inertia and surface tension force on the gelatin methacrylate (GelMA) pre- polymer droplet generation and droplet size were studied through experiments. Finally, based on computational and experimental results, the uniformly controlled size of GelMA microgels was created. All experimental data were summarized by a capillary number of the dispersed and the continuous phases to characterize the different regimes of GelMA pre-polymer droplet generation and to predict the transition of dripping to a jetting regime for GelMA pre-polymer in the flow-focusing device. Also, two types of cells, MCF-7 breast cancer cells, and 3T3 fibroblasts, were mixed in a 5 wt% GelMA pre-polymer solution used as dispersed phase. The uniform cell-laden GelMA microgels were fabricated and the cell viability was over 80%. In addition, a new method to create the polydimethylsiloxane (PDMS) circular channel was developed using a rapid and cheap 3D printing process. Due to the resolution limitation of 3D printing, the channels were elliptical, and subsequent liquid PDMS injection process was adopted to form fully circular channels.