The first volume of the series is both a simple introduction to the JetBrains MPS language workbench and a complete reference manual. This book explains the MPS programming paradigm and gradually introduces the reader to the many features of the MPS platform. The "MPS Language Workbench" may yet be the simplest way to discover MPS and the powerful new approach to programming that this tool offers. The Meta Programming System (MPS) is a new kind of tool called a Language Workbench that makes it easier and more fun to write programs. With traditional programming, it is common to choose one programming language to solve a problem and being limited by this choice. When working with MPS you can use and combine different languages to solve a problem. You can also create simple languages (e.g., Domain Specific Languages) or extend existing ones when the languages available do not exactly meet the evolving needs of the problem at hand. The languages that you create with MPS will integrate nicely with languages developed by others. MPS is open-source and can be obtained from http: //jetbrains.com/mps. This third edition describes MPS version 3.3.