We visualise developmental biology as the study ofprogressive changes that occurwithin cells, tissues and organisms themselves during their life span. A good exampleofa field ofdevelopmentalbiology in whichthis conceptis encapsulatedis thatofsomitogenesis. The somitewas identifiedas the primordialunit underlyingthe segmentedorganisationofvertebrates more than two centuries ago. The spectacular discoveries and achievements inmolecularbiologyin the last fifty years have created a gene-basedrevolution in both the sorts ofquestions as well as the approaches one can use in developmental biology today. Largely as a resultofthis, during the 20th and 21st centuries this simple structure, the somite, has been the focus ofa deluge ofpapers addressingmultipleaspectsofsomiteformation and patterning both at the cellularand molecular level. One ofthe mainreasons for suchinterest in the process ofsomitogenesis stems from the fact that it is such an exquisitelybeautiful example ofbiology working under strict temporal and spatial control in a reiterative manner that is highly conserved across the vertebrate classes. Our intention is that this book will be ofinterest to different kinds ofscientists, includingbasic researchers, pathologists, anatomists, teachersandstudentsworking in the fields ofcell and developmentalbiology. The nine chapterscoverawide array of topics that endeavour to capture the spirit of this dynamic and ever-expanding disciplineby integratingboth contemporaryresearchwith the classical embryological literaturethat concentratedon descriptionsofmorphologicalchanges inembryos and the interactionsofcells and tissues during development. Inso doingthey encompass the main aspects ofsomitogenesis across four vertebrate classes (frog, fish, mouse and chick) and the hope is that this will enable readers to acquire an appreciationof this developmentalprocess in all its facets.