Oleaginous microalgae are considered to be a potential major biofuel producer in the future since, under conditions of nitrogen deprivation, they are capable of containing high amounts of lipids, while consuming industrial CO2. These photosynthetic microorganisms are, however, rather different from the microorganisms usually used in biotechnology. In particular, predicting the behaviour of microalgal based processes is delicate because of the strong interaction between biology (microalgal development and respiration). and physics (light attenuation and hydrodynamics). This paper reviews existing models, and in particular the Droop model which has been widely used to predict microalgal behaviour under nutrient limitation. It details a model for raceways or planar photobioreactors, when both light and nutrients are limiting. The challenges and hurdles to improve microalgal culture process modelling and control in order to optimise biomass or biofuel production are then discussed. (C) 2011 Elsevier Ltd. All rights reserved.