Edgar Allen identified and outlined the role of female sex hormones and discovered estrogen in the early 1900s in the US. In 1923, Allen, through his research with mice, isolated the primary ovarian hormone, later renamed estrogen, from ovarian follicles and tested its effect through injections in the uterine tissues of mice. Allen’s work on estrogen, enabled researchers to further study hormones and the endocrine system.

Lysogenic bacteria, or virus-infected bacteria, were the primary experimental models used by scientists working in the laboratories of the Pasteur Institute in Paris, France, during the 1950s and 1960s. Historians of science have noted that the use of lysogenic bacteria as a model in microbiological research influenced the scientific achievements of the Pasteur Institute's scientists. Francois Jacob and Jacques Monod used lysogenic bacteria to develop their operon model of gene regulation, to investigate the cellular regulatory mechanisms of the lysogenic life cycle, and to infer the process of cellular differentiation in the development of more complex eukaryotes.

The Stazione Zoologica Anton Dohrn (Anton Dohrn Zoological Station) is a public research institute focusing on biology and biodiversity. Hereafter called the Station, it was founded in Naples, Italy, in 1872 by Anton Dohrn. The type of research conducted at the Station has varied since it was created, though initial research focused on embryology. At the turn of the twentieth century, researchers at the Station established the sea urchin (Echinoidea) as a model organism for embryological research. A number of scientists conducted experiments on embryos and embryonic development at the Station from the 1890s to the 1930s, including Hans Driesch, Jacques Loeb, Theodor Boveri, Otto Warburg, Hans Spemann and Thomas Morgan. Research completed during this time at the Station contributed to the study of experimental embryology and developmental biology and helped shape the history of embryology.

Isidore Geoffroy Saint-Hilaire studied anatomy and congenital abnormalities in humans and other animals in nineteenth century France. Under the tutelage of his father, Etienne Geoffroy Saint-Hilaire, Isidore compiled and built on his father's studies of individuals with developmental malformations, then called monstrosities. In 1832, Isidore published Histoire generale et particuliere des anomalies de l'organisation chez l'homme et les animaux (General and Particular History of Structural Monstrosities in Man and Animals), in which he defined the term teratology as the study of birth defects and deformities. Isidore Geoffroy Saint-Hilaire established teratology as a legitimate branch of scientific study.

Francois Jacob studied in
bacteria and bacteriophages at the Institut Pasteur in Paris, France,
in the second half of the twentieth century. In 1965, Jacob won the
Nobel Prize in Physiology or Medicine with Andre M. Lwoff and
Jacques L. Monod for their work on the genetic control of enzyme
synthesis. Jacob studied how genes control and regulate metabolic
enzymes in the bacterium Escherichia
coli (E. coli) and in lysogenic
bacterial systems. He contributed to theories of transcriptional gene
regulation, the operon model, and the distinction between structural
and regulatory genes. Jacob also introduced the concept of
bricolage (tinkering) in evolutionary biology.

In his essay Evolution and Tinkering, published in
Science in 1977, Francois Jacob argued that a common analogy
between the process of evolution by natural selection and the
methods of engineering is problematic. Instead, he proposed to
describe the process of evolution with the concept of
bricolage (tinkering). In this essay, Jacob did not deny the
importance of the mechanism of natural selection in shaping complex
adaptations. Instead, he maintained that the cumulative effects of
history on the evolution of life, made evident by molecular data,
provides an alternative account of the patterns depicting the
history of life on earth. Jacob's essay contributed to
genetic research in the late twentieth century that emphasized
certain types of topics in evolutionary and developmental biology,
such as genetic regulation, gene duplication events, and the genetic
program of embryonic development. It also proposed why, in future
research, biologists should expect to discover an underlying
similarity in the molecular structure of genomes, and that they
should expect to find many imperfections in evolutionary history
despite the influence of natural selection.

In 2006, Kazutoshi Takahashi and Shinya Yamanaka reprogrammed mice fibroblast cells, which can produce only other fibroblast cells, to become pluripotent stem cells, which have the capacity to produce many different types of cells. Takahashi and Yamanaka also experimented with human cell cultures in 2007. Each worked at Kyoto University in Kyoto, Japan. They called the pluripotent stem cells that they produced induced pluripotent stem cells (iPSCs) because they had induced the adult cells, called differentiated cells, to become pluripotent stem cells through genetic manipulation. Yamanaka received the Nobel Prize in Physiology or Medicine in 2012, along with John Gurdon, as their work showed scientists how to reprogram mature cells to become pluripotent. Takahashi and Yamanaka's 2006 and 2007 experiments showed that scientists can prompt adult body cells to dedifferentiate, or lose specialized characteristics, and behave similarly to embryonic stem cells (ESCs).

Georges Cuvier, baptized Georges Jean-Leopold Nicolas-Frederic Cuvier, was a professor of anatomy at the National Museum of Natural History in Paris, France, through the late eighteenth and early nineteenth centuries. Scholars recognize Cuvier as a founder of modern comparative anatomy, and as an important contributor to vertebrate paleontology and geology. Cuvier studied the form and function of animal anatomy, writing four volumes on quadruped fossils and co-writing eleven volumes on the natural history of fish with Achille Valenciennes. Moreover, Cuvier constructed a system of classification based on specific and well-articulated principles to help anatomists classify animal taxa. Cuvier had public debate in 1830 with Etienne Geoffroy Saint-Hilaire, a dispute centered on whether form or function matters most for the study of anatomy and whether the transmutation of organic forms can occur over time. Cuvier's opinions influenced the development of biology in France, and his arguments against transmutation of types influenced the reception of Charles Darwin's theory of evolution by natural selection among many French naturalists.