This work focuses on the effect of reaction conditions, in particular prepolymerization, on the particle morphology and how morphology influences process kinetics in the polymerization of heterophasic polypropylene. After establishing reproducibility and reference activity levels, a screening of the effect of homo and prepolymerization conditions on morphology was performed. Results showed for both catalysts studied, that prepo is required in order to obtain good activity and that addition of ethylene during prepolymerization is an effective handle to adjust the morphology. By addition of ethylene, bulk density of the resulting polymer is reduced and porosity is increased. Sorption measurements reveal for samples with lower bulk density faster mass-transfer rates. Activity in the matrix stage is for both catalysts basically not affected by ethylene in the prepo. Crystallinity of the homopolymers is not affected by ethylene in the prepo step. During the rubber-phase, the samples with ethylene in the prepo showed lower activities. There are indications that ethylene incorporation in the rubber step is higher for samples with ethylene during the prepolymerization. Simulation studies show that samples with ethylene in the prepo reduce the mass-transfer limitations for ethylene in the heco-stage, which helps to better exploit the catalyst capabilities for ethylene incorporation.