The Harvard Embryological Collection (HEC) is a prime example of a historic histological embryo collection. The HEC was started in the late 19th century by notable American anatomist Charles Sedgewick Minot. The collection is broadly systematic, including 60 taxa with at least several examples from every vertebrate class. It was founded in a collaborative spirit to provide the research community a “cyclopedia” to promote new research and provide reproducible staging in embryology. The collection was successful in spawning a number of seminal works in the field. Slides were prepared according to strict archival standards with the intention that HEC slides would act as permanent vouchers. However, the collection became dormant and unrecognized for most of the 20th century. The collection, now safely housed at the Museum of Comparative Zoology, is again available to researchers, and as its founders intended, it is still well preserved even after 100 years. It continues to serve as an archive for research of the early 20th century and it holds great value and promise to embryological research in the 21st.