The JetBrains Meta Programming System (MPS) is a Language Workbench or a programming environment which makes it easy to define your own specialized languages.
A language defined in MPS can only be used in the same workbench (or in a specifically tailored environment) together with other DSLs to develop solutions.
Any MPS language receives basic IDE support such as code completion and navigation, which can be further customized and enriched with specific refactorings, intentions, error highlighting and so on.
MPS language is not textual, and its definition is not based on a grammar.
A great advantage of this is that your language can be developed as a pretty isolated module and can then be mixed with other languages to create a blend which perfectly matches the problem domain.