Abstract: Very strong capillary forces combined with confinement contribute to the difficulty in the direct simulations of drops in microfluidic devices. In this talk, I'll present our recent combined asymptotic and numerical study of a simplified model for a dispersion which is pumped through a T-junction. The numerical method is based on a height-function formulation for a volume-of-fluid representation of the two liquids. Both the Bretherton and the Richardson bubble are used for benchmarking the code, thus establishing the degree of accuracy and robustness. The viscosity ratio of the drop to matrix liquid is varied to investigate the range of behavior from the presence of a bubble to that of a highly viscous drop. I will present our computational results of the drop breakup in a T-junction along with the asymptotic theory in the limit of low capillary number. If time permits, I'll show my recent numerical findings of drop breakup that has been observed in experimental data [Phys. Fluids 21, 072001 (2009)] when a large drop goes through a T-junction.