Girolamo Fabrici (Fabricius) is perhaps best known as the founder of the modern science of embryology. From 1600 until his death, he carried out important and original research on the late fetal stages of many different animals. In 1612, he published the first detailed description of the development of the chick embryo from the sixth day onward.

Fabricius made a number of additional advances in the field of anatomy. He studied the structure of the eye and of the larynx, the mechanics of respiration, and the movement of muscles. One of his most important accomplishments was his detailed description of the semilunar valves in veins. Although these valves had been observed earlier, Fabricius published the most complete description of their structure and function in his De venarum ostiolis (On the Valves of the Veins) in 1603. He was incorrect, however, in his explanation of the valves' function.

Girolamo (also Geronimo) Fabrici (also Fabrizio or Fabricius) was born in the town of Aquapendente, near Orvieto, Italy. He studied first humanities, then medicine, at the University of Padua. His teacher in anatomy and surgery was Gabriel Fallopius. After graduating with his M.D. in 1559, he taught anatomy privately and practiced surgery until 1565. In that year, he was appointed to replace Fallopius, who had died, at Padua. Fabricius held that post until 1613, when he retired because of ill health. He died in Bugazzi, near Padua, in 1619.

In addition to his scholarly work, Fabricius made other contributions. He attained considerable fame as a teacher. His most famous student was William Harvey, who studied with him from 1597 to 1602. In addition, Fabricius was instrumental in establishing the first permanent anatomical theater at the University of Padua.