Karl Wilhelm Theodor Richard von Hertwig is an important figure in the history of embryology for his contributions of artificial hybridization of sea urchin eggs and the formulation of his coelom theory. He was born 23 September 1850 in Friedelberg, Germany, to Elise Trapp and Carl Hertwig. Richard and his older brother Oscar began their studies at Jena under the direction of Ernst Haeckel from 1868 to 1871. In 1872 Hertwig became a lecturer in zoology at Jena while Oscar lectured in anatomy and embryology. As both brothers advanced in their respective fields, Hertwig left Jena to become a professor at Königsberg. In 1883 he was professor at Bonn and in 1885 in Munich, where he stayed until his retirement in 1925. Hertwig married Julia Braun in 1887 and had two sons and one daughter. He remained very active his entire life, outliving his brother Oscar by fifteen years.

James Marion Sims developed a surgical cure for ruptures of the wall separating the bladder from the vagina during labor, ruptures called vesico-vaginal fistulas, and he developed techniques and tools used to improve reproductive examinations and health care for women in the US during the nineteenth century. Sims's lateral examination position allowed doctors to better see the vaginal cavity, and his speculum, a spoon-like object used for increased view into the vagina, helped to make gynecological examinations more thorough. Sims helped ease the physical and social strains of post-birth women who suffered from vesico-vaginal fistulas, and he established the first hospital in New York City, New York, dedicated solely to treating women and improving women's health care.

Hans Spemann was an experimental embryologist best known for his transplantation studies and as the originator of the "organizer" concept. One of his earliest experiments involved constricting the blastomeres of a fertilized salamander egg with a noose of fine baby hair, resulting in a partially double embryo with two heads and one tail. Spemann continued changing variables such as the amount of time the embryo was constricted and the degree of constriction, all of which added more empirical evidence to Hans Driesch's studies showing that embryonic cells could self-regulate to varying degrees. Spemann's long list of "simple" experiments and significant findings were mainly carried out at his laboratory, the Spemann School at the University of Freiburg, Germany, where numerous graduate students collaborated with Spemann to investigate embryonic induction.

Libbie Henrietta Hyman was born into a recently immigrated Jewish family on 6 December 1888 in Des Moines, Iowa. One of many siblings and daughter to parents Sabina Neumann and Joseph Hyman, who did not particularly support her interests in science, Hyman excelled in school and indulged her interests in biology in her free time. From a young age, Hyman collected and cataloged flora around her home. Despite being valedictorian of her high school class, Hyman's first job was labeling cereal boxes in a local factory. It was only when a former teacher became aware of Hyman's situation that Hyman was prompted to apply for college scholarships.

Nicolaas Hartsoeker, a Dutch astronomer, optics manufacturer, and naturalist, was born 26 March 1656 in Gouda, Netherlands, and died 10 December 1725. His mother was Anna van der Mey and his father was Christiaan Hartsoeker, a prominent evangelical minister. His major contribution to embryology was his observations of human sperm cells, which he claimed to be the first to see under a microscope. His sketch of the homunculus, a tiny preformed human he believed to exist in the head of spermatazoa, is his lasting scientific legacy in the field of embryology. This sketch was only a minor part of his first publication, Essai de Dioptrique (1694), which dealt primarily with the use of optical lenses in science. In subsequent years the sketch became iconic of the theory of embryological development known now as preformationism. Hartsoeker himself was a vocal adherent of spermist preformationism and is often cited as the originator of the idea.

Wilhelm Roux was a nineteenth-century experimental embryologist who was best known for pioneering Entwicklungsmechanik, or developmental mechanics. Roux was born in Jena, Germany, on 9 June 1850, the only son of Clotilde Baumbach and a university fencing master, F. A. Wilhelm Ludwig Roux. Roux described himself as an aloof child, but when he was fourteen he cultivated a passion for science that was encouraged by the director at Oberrealschule in Meiningen. Roux attended the University of Jena in 1869, but his education was halted after the first year because of his service in the military during the Franco-Prussian War. When he returned from the war, he continued to take classes and was admitted into the University of Jena medical faculty. He passed his medical examination in 1877 and became a licensed doctor.

Carl Gottfried Hartman researched the reproductive physiology of opossums and rhesus monkeys. He was the first to extensively study the embryology and physiology of reproduction in opossums when little was known about this mammal. Hartman worked in Texas where opossums, the only marsupial that lives in North America, were abundant. The female opossum delivers her fetal opossums in her pouch, where one can easily observe their development. After studying opossums for thirteen years, Hartman investigated the reproductive physiology of rhesus monkeys, also known as macaques. This research led to the discovery of when ovulation occurs, as well as its relation to the human menstrual cycle. Later research on scientific methods of birth control relied heavily on Hartman 's discoveries about primate and human reproduction.

Rosalind Elsie Franklin worked with X-ray crystallography at King's College London, UK, and she helped determine the helical structure of DNA in the early 1950s. Franklin's research helped establish molecular genetics, a field that investigates how heredity works on the molecular level. The discovery of the structure of DNA also made future research possible into the molecular basis of embryonic development, genetic disorders, and gene manipulation.

The HeLa cell line was the first immortal human cell line that George Otto Gey, Margaret Gey, and Mary Kucibek first isolated from Henrietta Lacks and developed at The Johns Hopkins Hospital in Baltimore, Maryland, in 1951. An immortal human cell line is a cluster of cells that continuously multiply on their own outside of the human from which they originated. Scientists use immortal human cell lines in their research to investigate how cells function in humans. Though the HeLa cell line has contributed to many advancements in biomedical research since the twentieth century, its usage in medical research has been controversial because Lacks did not consent to having her cells used for such purposes. As of 2020, scientists continue to use the HeLa cell line for numerous scientific advancements, such as the development of vaccines and the identification of many underlying disease mechanisms.

Jacques Loeb experimented on embryos in Europe and the United States at the end of the nineteenth and beginning of the twentieth centuries. Among the first to study embryos through experimentation, Loeb helped found the new field of experimental embryology. Notably, Loeb showed scientists how to create artificial parthenogenesis, thus refuting the idea that spermatozoa alone were necessary to develop eggs into embryos and confirming the idea that the chemical constitution of embryos environment affected their development. Furthermore, Loeb' s work showed that scientists could manipulate materials in a laboratory to create, as he called the process, the beginning stages of life.