The major advantage of the avian embryo for the embryologist is its accessibility for manipulation and observation. Indeed, it is for this reason that, historically, detailed descriptions of normal development were first available for avian embryos, generally chick embryos (1). Artificial incubation and hatching of chicken eggs date to the time of the 18th dynasty in Egypt (ca. 1400 bc), and possibly even earlier in ancient China. The Egyptian practice of egg incubation is well documented in Roman literature, including references by Pliny, Diodorus Siculus, and in the letters of Emperor Hadrian. However, artificial incubation was lost throughout the Middle Ages and was only revived during the 18th century. The first recorded observations of avian embryos is included in the works attributed to Hippocrates (ca. 430 bc), although it was Aristotle who provided the first significant observations (Historia Animalium and De Generatione Animalium, ca. 350 bc). Detailed and illustrated accounts were published between the late 16th and 18th centuries written by Aldrovanus (Ornithologia, 1597) Fabricius (De Formatione Ovi et Pulli, 1604), Harvey (De Generatione Animalium, 1651), Shrader (Observations et Historiae, 1674), Malpighi (De Ovo Incubato and De Formatione Pulli in Ovo, 1672), Mayow (De Respiratione Foetus in Utero et Ovo, 1674), Maître-Jan (Observations sur la formation du poulet, 1722), and Haller (Sur la formation du coeur dans le poulet, 1767). The first attempts to incubate eggs with part of the shell removed to form a “window” were described by Beguelin (Memoir sur l’art de couver les oeufs overts, 1749).