JetBrains MPS is an integrated environment for language engineering. It allows language designers to define new programming languages, both general-purpose and domain-specific, either as standalone entities or as modular extensions of already existing ones. Since MPS leverages the concept of projectional editing, non-textual and non-parseable syntactic forms are possible, including tables or mathematical symbols. This tool paper introduces MPS and shows how its novel approach can be applied to Java development. Special attention will be paid to the ability to modularize and compose languages.