In this lecture we describe OpenSMT, an incremental, efficient, extensible and open-source SMT-Solver. OpenSMT has been specifically designed to be easily extended with new theory-solvers, in order to be accessible for non-experts for the development of customized algorithms. We sketch the solver's architecture and interface, and we discuss its distinguishing features w.r.t. state-of-the-art SMT-Solvers.