Embryology is a branch of biology that has an immediate bearing on the problem of
“life.” Life cannot be fully accounted for without an understanding of its dynamic
nature, which expresses itself in the incessant production of new organisms in the
process of ontogenetic development. Therefore, embryology is defined as the science
of the development of an embryo from the fertilization of the ovum to the fetus
stage. Teaching of embryology has long been an established feature at universities
throughout the world, both for students in biology and students in medical sciences.
During the twentieth century most of this science has been overshadowed by experimental-
based genetics and cell biology, which have turned classical embryology
into “developmental biology.” Several universities are now teaching developmental
biology instead of embryology as a course in biology programs. Significant contributions
made in the twenty-first century in the fields of molecular biology, biochemistry,
and genomics, integrated with embryology and developmental biology, provide
an understanding of the molecular portrait of a “developmental cell.” This integrated
approach to development is incorporated in the present book as “stem cell biology,”
a new sister branch of embryology/developmental biology that emphasizes the study
of self-renewal, differentiation, pluripotency, and nuclear programming, which are
characteristics of stem cells. In a broad sense, stem cell biology is nothing more than
an understanding of embryology and development together at the molecular level
using engineering, imaging, and cell culture principles. With such a wide scope, this
book can only be an introduction to stem cell biology.