Conrad Hal Waddington was an embryologist and theoretical biologist. His early experimental work investigated aspects of embryonic induction and the properties of the organizer first identified by Hans Spemann and Hilde Mangold, while his later studies focused on genetic assimilation. Waddington is probably best known for developing the concept of the epigenetic landscape, and he also held significant interest in many different areas ranging from the visual arts and poetry to philosophy. Throughout his career, Waddington maintained that the arts were integral to science, and he continued to draw inspiration from the arts for his own work.

Percivall Pott was a physician in England during the eighteenth century who identified soot as the cause of chimney sweeps' scrotal cancer, later called testicular cancer. In the 1770s, Pott observed that scrotal cancer commonly afflicted chimney sweeps, the young boys sent up into chimneys to clean away the soot left over from fires, and he hypothesized that the soot inside chimneys might cause that type of cancer. Pott was one of the first doctors to identify some environmental factor as causing cancer. Pott's research helped chimney sweeps to prevent scrotal cancer by using protective clothing, and it also allowed for future research on environmental causes of cancers.

Alexis Carrel was a doctor and researcher who studied tissue cultures. He continued Ross Granville Harrison's research and produced many improvements in the field of tissue culture and surgery. He was the recipient of the 1912 Nobel Prize in Physiology or Medicine for his development of surgical techniques to repair blood vessels. Carrel was born on 28 June 1873 in Sainte-Foy-les-Lyon, France, to Anne-Marie Ricard and Alexis Carrel Billiard. His father died when he was five years old. Carrel earned a bachelor's degree in letters in 1889 and another in science in 1890 from St. Joseph's Day School in Lyon, France. He entered medical school at the age of seventeen and was regarded as a good but not exceptional student. The assassination of Sadi Carnot, a French politician visiting Lyon who was stabbed in the abdomen and died from the loss of blood, further interested him in surgery.

Johannes Holtfreter made important discoveries about the properties of the organizer discovered by Hans Spemann. Although he spent much time away from the lab over many years, he was a productive researcher. His colleagues noted that the time he spent away helped revitalize his ideas. He is credited with the development of a balanced salt medium to allow embryos to develop; the discovery that dead organizer tissue retains inductive abilities; and the development of specification, competence, and distribution of fate maps in the developing frog embryo. He was the sole author on all but three of the more than sixty papers he published. Johannes Holtfreter was born on 9 January 1901 in Richtenberg, Germany. He was the middle of three children, the only boy, and grew up collecting and drawing butterflies and other animals in the surrounding area. When World War I began, his family moved to Strausland, Germany, to avoid the war.

Jane Maienschein is the daughter of Joyce Kylander and Fred Maienschein, and was born in Oak Ridge, Tennessee, on 23 September 1950. She attended MIT as a freshman and then transferred to Yale University in 1969 when Yale decided to admit women undergraduates. In 1972 she graduated with an honors degree in History, the Arts, and Letters having written a thesis on the history of science. She then attended Indiana University and studied with historian of embryology Frederick B. Churchill, took courses with embryologist Rudolf Raff, and learned how to do embryological laboratory research with Robert Briggs. She received her MA in 1976 and a PhD in 1978, with a pre-doctoral Fellowship at the Smithsonian to study the history of microscopes and microscopy, and an NSF-funded dissertation improvement visit to the Marine Biological Laboratory (MBL) to reproduce old embryological experiments and soak up the history and resources of the MBL Library and labs. Maienschein's scholarly research focuses on the history and philosophy of developmental biology.

Nicole Marthe Le Douarin was one of the first progressive female pioneers of developmental and embryological research. Some of her most notable and ground-breaking work involves grafting quail and chicken embryos together in order to study the developmental fate of each contributing embryo. Le Douarin was born in Brittany, France, on 20 August 1930. As an only child she was inspired by her mother, a school teacher at the time, to develop a passion for learning. According to Le Douarin her father was an open-minded businessman who, likely because she was an only child, raised her much like a boy. In 1944 Le Douarin was forced to move out of her hometown of Lorient and attend a boarding school in Nantes, France, to escape the invasion of German forces during World War II. After the war, she returned to her high school in Lorient, where she received her baccalaureate in 1949. During her last year in Lorient, when she was only seventeen, Douarin met her fianc_. After graduating, and against the wishes of her mother, she moved with him to Paris where they attended the Sorbonne. In 1951, after three years of courtship and university classes together, the couple was married. Le Douarin graduated from the Sorbonne with a degree in the natural sciences in 1954. Instead of immediately continuing to graduate school, she chose to teach science at a local high school and raise a family.

Pope Gregory XIV, born Nicolo Sfondrati, reversed the bull of Pope Sixtus V, Effraenatum, under which an abortion at any time of gestation can be punished by excommunication. He supported the Aristotelian distinction between an "animated" and "unanimated" fetus, making abortion of an unanimated fetus punishable by lesser means. This decision contributed to the historical debates within the Roman Catholic Church on when a fetus has a soul, and when abortion was punishable by excommunication.

Andrew Zachary Fire is a professor at Stanford University and Nobel Laureate. Fire worked at the Carnegie Institution of Washington's Department of Embryology in Baltimore, Maryland, with colleague Craig Mello, where they discovered that RNA molecules could be used to turn off or knock out the expression of genes. Fire and Mello called the process RNA interference (RNAi), and won the Nobel Prize in Physiology or Medicine in 2006 for their discovery.

Charles Otis Whitman was an extremely curious and driven researcher who was not content to limit himself to one field of expertise. Among the fields of study to which he made significant contributions were: embryology; morphology, or the form of living organisms and the relationships between their structures; natural history; and behavior. Whitman served as director of several programs and institutions, including the Biology Department at the University of Chicago, where he helped establish a new style of biology and influenced the work of many researchers of his generation, as well as future ones. He also served as first director of the Marine Biological Laboratory (MBL) in Woods Hole, MA. Besides his considerable achievements with his own scientific research, Whitman was a tireless mentor who had many students who went on to achieve great success in the field of embryology.

Robert Geoffrey Edwards worked with Patrick Christopher Steptoe to develop in-vitro fertilization (IVF) techniques during the 1960s and 1970s in the United Kingdom. Louise Brown, the world' s first "test-tube baby," was born as a result of Edwards and Steptoe's IVF techniques in 1978, and since then more than four million children have been born using IVF techniques. Publicity and controversy accompanied Edwards and Steptoe's work as conservative religious institutions expressed concern over the morality of the IVF procedure. Edwards was honored for his accomplishments, receiving numerous awards including the 2010 Nobel Prize in Physiology or Medicine.