This book gives a brief introduction to origin of MCRs, and exemplifies various reported multi-component reactions and catalysts employed. Four different approaches (SRR, MRS, CBD and MCR2) have been applied, which all led to the development of new MCRs and higher order MCRs, thereby addressing both molecular diversity and complexity. The book characterized the framework considering of chapters prepared by the index, List of abbreviation and general introduction. Authors expected this book to contribute to this trend and multi component reactions.