We present the marmoteCore software, an open environment for modeling with Markov chains, developed within the MARMOTE project. 1 This platform aims at providing the general scientific user with tools for creating Markov models and computing, or simulating, their behavior. It provides a software library implementing both basic models and methods “from the book” and advanced solution methods : either general, or for specific classes of models. marmoteCore is devised to be a collaborative platform, able to embed solution methods and software developed by independent teams. We describe its architecture and some of its features, including its capability to communicate with established scientific software such as R.