Integration of multiple languages into each other and into an existing development environment is a difficult task. As a consequence, developers often end up using only internal DSLs that strictly rely on the constraints imposed by the host language. Infrastructures do exist to mix languages, but they often do it at the price of losing the development tools of the host language. Instead of inventing a completely new infrastructure, our solution is to integrate new languages deeply into the existing host environment and reuse the infrastructure offered by it. In this paper we show why Smalltalk is the best practical choice for such a host language.