"Animal Cell Technology: Challenges for the 21st Century" is a comprehensive technical book that addresses the growing discipline of animal cell technology. This discipline aims to understand the structures, functions, and behaviors of differentiated animal cells and to explore their applications in industrial and medical fields. The book discusses the clonal expansion of differentiated cells, the optimization of their culture conditions, and the modulation of their ability to produce important medical and pharmaceutical proteins. Additionally, it covers the use of animal cells in gene therapy and artificial organs. The insights compiled in this volume provide a complete overview of the current state of the art in Japan and are aimed at professionals from various disciplines, including cell biologists, biochemists, molecular biologists, and biochemical engineers working in academic or industrial settings.