MOSILAB from the Fraunhofer-Gesellschaft is a newly developed Modelica simulator for complex technical systems. One innovative feature of MOSILAB is the mapping of state-dependent changes of the model structure during the simulation experiment. This enables, for example, simulation experiments with models of variable modeling depth or varying model physics. The current MOSILAB Version is 4, this version is not released and only used on intern projects. The TU Berlin is currently working on ideas for the Version 5 of MOSILAB. This version is planned to support the new Modelica Specification 4 and thus will not be released anytime soon. The current developments can be seen on the new MOSILAB Website.