During the last decade, modern technologies have made a revolutionary change in developmental biology. The molecular and cellular processes in live embryos can now be visualized thanks to technologies using fluorescent proteins. The whole genome information of a wide range of animal species has now become available, confirming the common principles that operate in every species. These and other advances in our understanding of the developmental processes during embryogenesis and tissue regeneration have put forward new principles. Those new principles will also be important in the stem cell biology, branched from developmental biology, in order to generate a particular tissue by manipulating stem cells. This book is planned to introduce these new principles to readers who are working in developmental biology and/or stem cell biology fields, with an emphasis on genetic and cellular processes.