SPIS Open-Source Code: Methods, Capabilities, Achievements, and Prospects. In this paper, recent improvements in the modeling capabilities of the Spacecraft Plasma Interaction Software (SPIS) code are presented. New developments still in progress are also reported. They should in particular allow modeling of fast dynamical phenomena, including processes as challenging as the second part of ESDs, i.e., the vacuum arc and its related flashover plasma expansion. The first, electronic, part of ESDs is already modeled. The range of SPIS application domains and studies is reviewed. An interesting study case, the assessment of charging at multiple-scale levels, is presented here in more detail. Charging in geostationary-Earth-orbit conditions is simulated from the spacecraft scale down to a solar-cell-gap (hence, decameters to millimeter) scale. This self-consistent computation shows that macroscopic inverted-voltage-gradient (IVG) cases may differ at microscopic scales close to a solar-cell gap, due to the local blocking of secondary emission by the small-scale electric-field configuration. We consider this effect as the likely origin of the different ESD triggering thresholds, depending whether IVG is obtained by electrons or plasma.