<p>Earlier narrations in this series discussed the genesis of cell theory, how new paradigms of experimental approaches emerged during the later part of the 19th century that unraveled connections between chromosomes, genes, and gene products [1–4]. During this period, descriptive embryology was also supplemented by experimental embryology to understand the mechanisms underlying embryonic development. The present article examines, primarily using examples from studies on animal development, how embryology evolved into developmental biology. Interestingly, while leading experimental embryologists like E. B. Wilson, Theodor Boveri, and Thomas Hunt Morgan of the late 19th century contributed maximally to the early growth of the emerging field of genetics, the fields of embryology and genetics remained segregated, often with some mutual dislike, till almost the 4th decade of the last century. The subsequent integration of embryology, genetics, biochemistry, evolution, etc., heralded the transformation of embryology and emergence of fields variously named as ‘developmental biology’, ‘developmental genetics’, and ‘evo-devo’. These dynamic areas of research have transformed biology by providing remarkable insights into intra- and inter-cellular physico-chemical as well as mechanical interactions that underlie morphogenesis and evolution.</p>