Tissue grafts obtained from tissue engineering techniques can be developed with the application of cells in a scaffold within a bioreactor. In this chapter we present a multiscale method to simulate a bioreactor design that can adapt to the personalized tissue sought. It includes personalization of the bioreactor design but also personalization of the in vitro conditions. As the research area is going further and the computational possibilities as well, tools must be developed to design patient’s cell-specific pair of scaffold and bioreactor, as a virtual physiological human cell tool. Thanks to a parametric geometry and a computational fluid dynamics model, we are able to design bioreactor chambers relying on the nearest boundary conditions in the bones to apply it to the bone substitute where cells have been seeded. First of all, considering an existing bioreactor chamber, we can design an optimized scaffold knowing the boundary conditions that the bioreactor chamber will impose. On the other hand, knowing the scaffold geometry used, a bioreactor chamber will be designed to reach appropriate environmental conditions at the cell scale. It allowed testing two different bioreactor geometries showing no major interest within the simulation, but regarding the experimental process, the bubble traps presence is compulsory to avoid cell death. On the other hand, two scaffold geometries were tested highlighting a major difference regarding the local fluid flow within the scaffold pores and therefore on the cell development. Moreover, experimental analyses are required to correctly compare the simulation and improve the strength of the optimization process.