The investigation of the atomistic mechanisms of crystal nucleation constitutes a major challenge to both experiment and theory. Understanding the underlying principles of composite materials formation represents an even harder task. For the investigation of the mechanisms of crystal nucleation a profound knowledge of the ion-solvent and the ion-ion interactions in solution is required. Studying biocomposites like fluorapatite-collagen materials, we must furthermore account for the biomolecules and their effect on the growth process. Molecular simulation approaches directly offer atomistic resolution and hence appear particularly suited for detailed mechanistic analyses. However, the computational effort is typically immense and for a long time the investigation of crystal nucleation from atomistic simulations was considered as impossible. We therefore developed special simulation strategies, which allowed to considerably extent the limitations of computational studies in this field. In combination with advanced experimental investigations this provided new insights into the nucleation of biomimetic apatite-gelatin composites and the mechanisms of hierarchical growth at the micro- and mesoscopic scale. Along this line, molecular simulation studies reflect a powerful tool to achieve a profound understanding of the complex growth processes of apatite/collagen composites. Apart from reviewing related work we outline future directions and discuss the perspectives of simulation studies for the investigation of biomineralization processes in general.