The development of a new organ is the result of coordinated events of cell division and expansion, in strong interaction with each other. This paper presents an improved version of a tomato model, which includes cells division, endoreduplication and expansion processes. The model is used to investigate the interaction among these developmental processes, in the perspective of a new cellular theory. In particular, different control schemes (either cell- or organ-based) are tested and simulation results are compared to observed data. The model shows that a pure cell-based control fails to reproduce the observed cell size distribution, and an organ-based control is needed in order to get realistic cell and fruit sizes. The model also supports the role of endoreduplication as an important modulator of the cell expansion potential.