In the last chapter, a general approach to include an alien subsystem into a distributed system was introduced. Current contribution from those "inserted" systems is integrated with the surface integration for the magnetic field in (7.3); therefore, the interaction between the distributed system and the inserted subsystem could be simulated. Lumped components and their simple combination are illustrated to be included in the analysis of distributed system, using the constitutive equations of the lumped systems. As another application example to demonstrate the versatility of the general modeling approach, movements of charged particles in a planar diode and in space are modeled in FDTD simulation. Possible applications for hybrid cosimulation of charged particles and an electromagnetic field include analysis of some semiconductor microvacuum devices. As yet another application example, in a later chapter, current from a nonlinear active gain medium is included in the FDTD simulation for optical cavity mode and circuit analysis. As the needs for hybrid system simulation flourish, the general hybrid system modeling approach should provide an excellent bridge between a distributed electrical system and other current-contributing systems.