  Some prescriptions for in-medium complex particle production in nuclear
reactions are proposed. They have been implemented in two models to simulate
nucleon-nucleus (nIPSE) and nucleus-nucleus (HIPSE) reactions around the Fermi
energy \cite{Lac04,Lac05}. Our work emphasizes the effect of randomness in
cluster formation, the importance of the nucleonic Fermi motion as well as the
role of conservation laws. The key role of the phase-space exploration before
and after secondary decay is underlined. This is illustrated in the case of two
debated issues: the memory loss of the entrance channel in central collisions
and the $(N,Z)$ partitions after the pre-equilibrium stage.
