This textbook is written with the primary aim to understand the overall mechanisms of invasion and metastasis in a more simplified manner. This book explains in detail about the evolution and pathogenesis of metastasis. The cancer cells that travel through the body are capable of establishing new tumors in distant location from the site of primary tumor. To metastasize, a cancer cells must break away from its primary site and enter into circulatory or lymph system which will carry it to a new location and establish itself in the new site. Further, a note on molecular pathogenesis and signaling pathways are added for a better understanding of metastasis with colour plates.