The embryological treatise De formatione ovi et pulli (On the Formation of the Egg and of the Chick) was written by anatomist and embryologist Girolamo Fabrici and published in Padua posthumously in 1621. The book was edited by Joahannes Prevotius and is separated into two parts that describe Fabrici's observations and assumptions on embryology and combine the traditional knowledge of his predecessors with his own first-hand anatomical observations. Each part is separated into three chapters: the first part concerns the formation of the egg while the second part of the treatise covers the generation of the chick within the egg.

The embryological treatise De formato foetu (The Formed Fetus) was written by anatomist and embryologist Girolamo Fabrici. There is no conclusive evidence regarding the first date of publication and what is listed on many copies ranges from 1600-1620, with speculation that the dates were altered by hand. Most forms of the book are dated 1600 and were issued by Franciscus Bolzetta who sold many copies in Venice and whose name appears on the engraved title-page. There is also verification of the book being printed in Padua by Laurentius Pasquatus in 1604. This treatise was the last publication to be issued before Fabrici retired from his teaching position at the Univeristy of Padua and it was the last anatomical work of his to be published during his lifetime. The book illustrates Fabrici's views on the anatomy of the fetus and uterus and demonstrates his struggle between accepting traditional authority and relying on his own experience in his investigations in embryology.

Girolamo Fabrici, known as Hieronymus Fabricius in Latin, was given the surname Aquapendente from the city where he was born, near Orvieto, Italy. Born in 1533, Fabrici was the eldest son of a respected noble family, whose coat of arms appears as an illustration in the title page of Fabrici's book on embryology, De formato foetu. Little is known of Fabrici's parents. His father is recorded as Fabricio, and Fabrici is said to have been named for his paternal grandfather. Fabrici influenced many scientists and physicians of his time to consider embryology as a legitimate and independent subject, and his two illustrated treatises on embryology are a remarkable legacy of his investigations on the development and comparative anatomy of fetuses.

Leonardo da Vinci was born on 15 April 1452, the illegitimate son of a young peasant girl by the name of Caterina and Ser Piero da Vinci, a well-renowned Florentine notary. Leonardo lived in Italy in the town of Vinci until his late teens and received a simple education in reading and writing as well as some training in mathematics and engineering. Although he was socially excluded by birthright from almost every profession and prohibited from attending any formal university, Leonardo went on to become a celebrated scientist, artist, and engineer. His research in mathematics, mechanics, cosmology, hydrodynamics, biology, botany, geology, geography, and anatomy signify his ingenious skills as a polymath. Among his numerous contributions, Leonardo is most famous for his artwork, anatomical drawings, and imaginative mechanical structures that influenced his natural philosophy and served to frame his early embryological studies. His embryological annotations and drawings of the fetus represent his groundbreaking curiosity and scientific method in depicting the human form in utmost detail.