A comprehensive review of modeling of evaporation and combustion of liquid fuel droplets using "unit cell" approach is presented. The review starts with a general introduction to the different regimes of droplet combustion and a brief overview of other techniques used for evaluating mutual interaction of droplets before presenting the cell model in detail. In this review, the major developments in this approach, encompassing effects of gas-phase convection, high pressure, and multicomponent composition of fuels, are reviewed for both dense and dilute sprays.