Miniature reactors are important devices used for process intensification. They provide a larger surface-to-volume ratio and enhance mass transfer and heat transfer significantly. This paper presents a review of transport processes of gas-liquid and liquidliquid two-phase flow in miniature geometries, in which the hydraulic diameter of the channel lies between 0.2 mm to 3.0 mm. Correlations for predict-ing the pressure drop in case of both adiabatic and non-adiabatic gas-liquid flows are summarized. Gas-liquid distributions are observed to be different from liquid-liquid flow distributions. Cross-sectional geometry does not have any effect on the flow regimes in this range. In case of liquid-liquid flow, the wall material plays an important role on flow distribution.