This document summarizes and describes the main building blocks of the Car2X Communication System as it is pursued by the Car2Car Communication Consortium (C2C-CC). “Car2X” means interactions among cars, between cars and infrastructures, and viceversa. It provides interested readers with an introduction to Car2X communications. It is intended to be a living document which will be complemented according to the progress of the work of the C2C-CC. One main objective of this document is to give insight into ongoing and upcoming activities, such as public funded projects which target to contribute to the C2C-CC specifications, an overview on ongoing work and results achieved so far. In addition, this document provides concepts and technologies that have been developed or identified by the C2C-CC and assessed as necessary building blocks to be proposed for a standard