Albert William Liley advanced the science of fetal physiology and the techniques of life-saving in utero blood transfusions for fetuses with Rh incompatibility, also known as hemolytic disease. Due to his advances, fetuses too young to survive premature delivery, and likely to die in utero if their Rh incompabilities were left untreated, were successfully transfused and carried to term. Liley was as passionate as a clinician and researcher as he was about his views on the rights of the unborn.

Sir John Bertrand Gurdon further developed nuclear transplantation, the technique used to clone organisms and to create stem cells, while working in Britain in the second half of the twentieth century. Gurdon's research built on the work of Thomas King and Robert Briggs in the United States, who in 1952 published findings that indicated that scientists could take a nucleus from an early embryonic cell and successfully transfer it into an unfertilized and enucleated egg cell. Briggs and King also concluded that a nucleus taken from an adult cell and similarly inserted into an unfertilized enucleated egg cell could not produce normal development. In 1962, however, Gurdon published results that indicated otherwise. While Briggs and King worked with Rana pipiens frogs, Gurdon used the faster-growing species Xenopus laevis to show that nuclei from specialized cells still held the potential to be any cell despite its specialization. In 2012, the Nobel Prize Committee awarded Gurdon and Shinya Yamanaka its prize in physiology and medicine for for their work on cloning and pluripotent stem cells.

Francesco Redi, son of Florentine physician Cecilia de' Ghinci and Gregorio Redi, was born in Arezzo, Italy, on 18 February 1626. He studied philosophy and medicine at the University of Pisa, graduating on 1 May 1647. A year later, Redi moved to Florence and registered at the Collegio Medico. There he served at the Medici Court as both the head physician and superintendent of the ducal pharmacy and foundry. Redi was also a member of the Accademia del Cimento, which flourished from 1657-1667. It was during this decade that Redi produced his most important works.

As one of the researchers involved in the development of the oral contraceptive pill, Min Chueh Chang helped to revolutionize the birth control movement. Although best known for his involvement with "the pill," Chang also made a number of discoveries throughout his scientific career involving a range of topics within the field of reproductive biology. He published nearly 350 articles in scientific journals. His dedication to his work left him with little time for family responsibilities, although shortly after his arrival in the United States in 1951, Chang married Isabelle Chin, an American-born Chinese woman with whom he would later have three children.

William Stewart Halsted was a surgeon at Johns Hopkins Hospital in Baltimore, Maryland, during the late 1800s and early 1900s. In 1894 Halsted described his procedure for treating breast cancer by removing the breast tissue, chest muscles, and lymph nodes in the armpit, a procedure he named radical mastectomy, and that became the standard of care for treating breast cancer until 1970. He also made contributions to other novel medical procedures such as gallbladder surgery, blood transfusions, antiseptic techniques, anesthesia use, and using plates and screws to hold bones in position when setting bone fractures. At Johns Hopkins Hospital, Halsted established a surgical training program in which he allowed medical students and surgical residents to shadow him and perform procedures under his guidance. In the twentieth century, similar training programs spread across the country and informed the standardization of medical training. Halsted devised a surgical treatment for breast cancer and reshaped the way physicians practiced medicine in the twentieth century, which resulted in better health outcomes through more careful surgical methods, especially in women with breast cancer.

"Casti Connubii," a papal encyclical given by Pope Pius XI on 31 December 1930, served primarily as a reaffirmation and expansion of the issues discussed in Arcanum, an encyclical written by Pope Leo XIII. It was released to address new threats to marriage and conjugal unity, and indeed is translated "On Christian Marriage" or "On Chastity in Marriage." The document explores the meaning of Christian marriage and emphasizes its threefold purpose as borrowed from St. Augustine: to produce offspring, to grow in conjugal faith, and to show benefit from the sacrament. It begins by exploring the nature of marriage, followed by a discussion of its advantages for individuals and societies, erroneous but common beliefs about marriage, threats to pure marriage, and finally how to address them. Included in the threats to pure marriage is that of the growing popularity of contraception and abortive procedures, at which point Pope Pius XI elaborates on the Church' s statement that life begins at conception.

During the 1870s and early 1880s, the British morphologist Francis Maitland Balfour contributed in important ways to the budding field of evolutionary embryology, especially through his comparative embryological approach to uncovering ancestral relationships between groups. As developmental biologist and historian Brian Hall has observed, the field of evolutionary embryology in the nineteenth century was the historical ancestor of modern-day evolutionary developmental biology. Balfour's work was notably inspired by Charles Darwin's theory of evolution and Ernst Haeckel's account of the relationships between embryology and evolution. Only a decade after Balfour's program of research began, an alpine climbing accident robbed Britain of its most promising embryologist.

Franklin Paine Mall was born into a farming family in Belle Plaine, Iowa, on 28 September 1862. While he attended a local academy, an influential teacher fueled Mall's interest in science. From 1880-1883, he studied medicine at the University of Michigan, attaining his MD degree in 1883. William J. Mayo, who later became a famous surgeon and co-founder of the Mayo Clinic in Rochester, Minnesota, was a classmate of Mall's. Throughout his studies at Michigan, he was influenced by Corydon L. Ford, a professor of anatomy, Victor C. Vaughn, a biochemist and bacteriologist, and Henry Sewall, a physiologist.