Florence Rena Sabin was born on November 9, 1871 in Central City, Colorado, the second daughter of George K. Sabin, a mining engineer, and Serena Miner Sabin, a schoolteacher. Her mother died of puerperal fever when Sabin was seven. She and her older sister Mary grew up in Denver, in Chicago with their uncle Albert Sabin, and in Vermont with their paternal grandparents. Both attended Vermont Academy, and were encouraged to go on to college.

Florence showed an early talent for math and science, but until high school she hoped for a career as a pianist. She directed her energies toward academic studies only after a classmate bluntly informed her that her musical talent was merely average. At Smith College (which her sister also attended) she majored in zoology, and was encouraged by the college physician to study medicine at Johns Hopkins' new co-educational medical school. She received her B.S. from Smith College in 1893, then taught high school for three years to earn enough to fund her first year of medical training.

Sabin entered the Johns Hopkins School of Medicine in 1896, one of fourteen women in a class of forty-five. Her skill and originality in laboratory classes attracted the attention of anatomist Franklin P. Mall, one of Hopkins' outstanding scientists. Mall became Sabin's mentor, advocate, and intellectual role model, encouraging her pursuit of "pure"(rather than applied) science, and suggesting two projects which would help establish her research reputation. One of these was a three-dimensional model of a newborn baby's brainstem, which became the basis of a widely used textbook, An Atlas of the Medulla and Midbrain, published in 1901. The other project was an investigation of the embryological development of the lymphatic system.

After a year's internship at the Johns Hopkins Hospital, Sabin won a research fellowship from the Baltimore Association for the Promotion of University Education for Women, and subsequently published two well-received papers. In 1902, she became the first woman faculty member at Johns Hopkins, teaching embryology and histology in the Department of Anatomy. She was promoted to associate professor in 1905, and to full professor in 1917, becoming the first woman to hold that rank at Johns Hopkins.

Sabin stayed on the faculty at Johns Hopkins until 1925, and during that time distinguished herself both as a researcher and a teacher. She did important work on the origins of the lymphatic system, demonstrating (by injecting colored substances into the lymphatic channels) that its structures were formed from the embryo's veins rather than from other tissues, as other researchers believed. She also investigated the origins of blood vessels, blood cells, and connective tissue. To do this, she perfected the technique of supravital staining, which allowed the study of the living cells. In 1924, she became the first woman president of the American Association of Anatomists, and the next year, the first woman elected to membership in the National Academy of Sciences.

Although she was an inspiring teacher and enjoyed working with her students, by the early 1920s, Sabin was longing to devote her full energies to her research. In late 1923, Simon Flexner, director of the Rockefeller Institute for Medical Research, invited her to join the Institute, and head its Department of Cellular Studies. She accepted his offer, and began her work there in 1925, the first woman to be appointed a full member at the Rockefeller Institute.

At the Rockefeller Institute, Sabin led research on the pathology of tuberculosis. Her team was part of a consortium of researchers working with the Medical Research Committee of the National Tuberculosis Association. During her thirteen years at Rockefeller, Sabin made major contributions to the understanding of tuberculosis, in particular by close study of the immune system responses to various chemical fractions isolated from the tuberculosis bacteria. Between 1930 and 1934, she also wrote a biography of her mentor, Franklin P. Mall, who had died in 1917.

In 1938, Sabin retired from the Rockefeller Institute and moved back to Colorado to live with her sister Mary. She maintained a lively correspondence with her research colleagues, attended conferences, and served on various advisory and governing boards for organizations such as the Guggenheim Foundation. In 1944, she was asked to chair the Health Committee of Colorado's Post-War Planning Committee. This committee investigated health services in the state, drafted a series of health bills later known as the "Sabin Program," and then campaigned for their passage. Four of the six bills were passed in 1947. After this, Sabin served as chair of an Interim Board of Health and Hospitals of Denver, and then as Manager of the Denver Department of Health and Charities until 1951. In the latter post, she launched a vigorous campaign to clean up the city, improve its sanitation, enforce health regulations for restaurants and food suppliers, and screen the population for tuberculosis and syphilis. Within two years, Denver's tuberculosis incidence was reduced from 54.7 to 27 per 100,000, and the syphilis frequency from 700 to 60 per 100,000.

Sabin was probably the best-known American woman scientist of her era, and received many awards and honors during her life. In 1929 the popular magazine, Pictorial Review, gave her its Annual Achievement Award; a Good Housekeeping poll in 1931 selected her as one of the twelve most eminent American women; she received Chi Omega sorority's National Achievement Award (1932), Bryn Mawr College's M. Carey Thomas Prize (1935), and fifteen honorary doctorates. In 1945, she received the Trudeau Medal of the National Tuberculosis Association for her earlier work on that disease. In 1951, she received the Lasker Foundation's Public Service Award for her public health work in Colorado. The same year, the Medical School of the University of Colorado dedicated a new biological sciences building in her honor. In 1959 the State of Colorado honored her by placing a statue of Sabin in the National Statuary Hall of the U.S. Capitol.

Such honors acknowledged Sabin's substantial scientific and public health achievements, of course, and some also lauded her for being a role model for women in the professions. Colleagues, students, and friends, however, also praised her personal warmth, her professional and personal generosity, her infectious energy, curiosity, and passion for scientific investigation. Sabin's correspondence reveals all these facets, as well as her love for classical music, philosophy, travel, good books, and memorable dinner parties.

Sabin's publications include over 100 scientific papers, several book chapters, two books--her Atlas of the Medulla and Midbrain and her biography of Franklin Mall--and numerous presentations.

Sabin died on October 3, 1953, in Denver.