The Law of Acceleration of Growth is a theory proposed by Edward Drinker Cope in the US during the nineteenth century. Cope developed it in an attempt to explain the evolution of genera by appealing to changes in the developmental timelines of organisms. Cope proposed this law as an additional theory to natural selection. He argued that the evolution of genera, the more general groups within which biologists group species, occurs when the individual in a species move through developmental stages faster than did their ancestors, but within the same fixed period of gestation, and thus can undergo new developmental stages and develop new traits. The Law of Acceleration compliments Cope's Law of Retardation of Growth. He described the later law as the process by which organisms revert to an ancestral stage. In these cases, forces suppress the most recent traits or stages common to the development of individuals from different species within the same genus. Cope described evolution as progressive, following a predetermined path, a perspective about evolution sometimes called orthogenetic. Cope's was one among many orthogenic theories in the second half of the nineteenth century. Furthermore, the theory was part of a trend in nineteenth century in which some biologists claimed that the changes in developmental timing of organisms could explain large changes in biological forms throughout natural history.

Cellular automata (CA) are mathematical models used to simulate complex systems or processes. In several fields, including biology, physics, and chemistry, CA are employed to analyze phenomena such as the growth of plants, DNA evolution, and embryogenesis. In the 1940s John von Neumann formalized the idea of cellular automata in order to create a theoretical model for a self-reproducing machine. Von Neumann's work was motivated by his attempt to understand biological evolution and self-reproduction.

The French flag model represents how embryonic cells receive and respond to genetic information and subsequently differentiate into patterns. Created by Lewis Wolpert in the late 1960s, the model uses the French tricolor flag as visual representation to explain how embryonic cells can interpret genetic code to create the same pattern even when certain pieces of the embryo are removed. Wolpert's model has provided crucial theoretical framework for investigating universal mechanisms of pattern formation during development.

In 2004, Amanda J. Drake and Brian R. Walker published “The Intergenerational Effects of Fetal Programming: Non-genomic Mechanisms for the Inheritance of Low Birth Weight and Cardiovascular Risk,” hereafter, “The Intergenerational Effects,” in the Journal of Endocrinology. In their article, the authors assert that cardiovascular disease may develop via fetal programming, which is when a certain event occurring during a critical point of pregnancy affects the fetus long after birth. Drake and Walker were among the first to show that the programming effects of cardiovascular disease could be sustained across generations through non-genetic means. In “The Intergenerational Effects,” the authors identify how non-genetic mechanisms may perpetuate fetal programming influences over generations, highlighting the importance for further research on fetal programming.

In 2001, researchers Leonie Welberg and Jonathan Seckl published the literature review “Prenatal Stress, Glucocorticoids, and the Programming of the Brain,” in which they report on the effects of prenatal stress on the development of the fetal brain. The fetus experiences prenatal stress while in the womb, or in utero. In discussing the effects of prenatal stress, the authors describe prenatal programming, which is when early environmental experiences permanently alter biological structure and function throughout life. Throughout “Prenatal Stress, Glucocorticoids and the Programming of the Brain,” Welberg and Seckl provide a number of potential biological explanations, derived from both animal and human studies, to explain the underlying mechanisms involved in programming, which helped establish how in utero stress can affect fetal brain development.

Spermism was one of two models of preformationism, a theory of embryo generation prevalent in the late seventeenth through the end of the eighteenth century. Spermist preformationism was the belief that offspring develop from a tiny fully-formed fetus contained within the head of a sperm cell. This model developed slightly later than the opposing ovist model because sperm cells were not seen under the microscope until about 1677. Spermism was never as dominant as ovist preformationism, but it had ardent followers whose work and writings greatly influenced the development of embryology in this time period. Spermism was and is now sometimes referred to as animalculism, a name taken from the term most naturalists at the time used to refer to microscopic organisms, or vermiculism, which comes from a specific term for sperm cells referring to their worm-like appearance. The most notable spermist philosophers and scientists were Nicolaas Hartsoeker, Anton Leeuwenhoek, and Wilhelm Gottfried Liebniz.

Frederik Ruysch, working in the Netherlands, introduced the term epithelia in the third volume of his Thesaurus Anatomicus in 1703. Ruysch created the term from the Greek epi, which means on top of, and thele, which means nipple, to describe the type of tissue he found when dissecting the lip of a cadaver. In the mid nineteenth century, anatomist Albrecht von Haller adopted the word epithelium, designating Ruysch's original terminology as the plural version. In modern science, epithelium is a type of animal tissue in which cells are packed into neatly arranged sheets. The epithelial cells lie proximate to each other and attach to a thin, fibrous sheet called a basement membrane. Epithelia line the surfaces of cavities and structures throughout the body, and also form glands. Although they lack blood vessels, epithelia contain nerves and can function to receive sensation, absorb, protect, and secrete, depending on which part of the body the epithelia line. During development, epithelia act in conjunction with another tissue type, mesenchyme, to form nearly every organ in the body, from hair and teeth to the digestive tract. Epithelia are an essential part of embryonic development and the maintenance and function of the body throughout life.

Ovism was one of two models of preformationism, a theory of generation prevalent in the late seventeenth through the end of the eighteenth century. Contrary to the competing theory of epigenesis (gradual emergence of form), preformationism held that the unborn offspring existed fully formed in the eggs or sperm of its parents prior to conception. The ovist model held that the maternal egg was the location of this preformed embryo, while the other preformationism model known as spermism preferred the paternal germ cell, as the name implies.

Introduced by Conrad Hal Waddington in 1942, the concept of epigenetics gave scientists a new paradigm of thought concerning embryonic development, and since then has been widely applied, for instance to inheritable diseases, molecular technologies, and indeed the human genome as a whole. A genome contains an embedded intricate coding template that provides a means of genetic expression from the initial steps of embryonic development until the death of the organism. Within the genome there are two prominent components: coding (exons) and non-coding (introns) sequences. Exons provide coding by transcribing a gene into a protein, while introns do not have this capacity. On top of these coding sequences lie mechanisms that dictate the overall capability of a gene without changing the underlying nucleotide sequence of DNA; these mechanisms are primarily known as epigenetic factors.

This embryology image is a pencil sketch by Nicolaas Hartsoeker, published as part of his 1694 French-language paper entitled Essai de Dioptrique, a semi-speculative work describing the sorts of new scientific observations that could be done using magnifying lenses. Dioptrique was published in Paris by the publishing house of Jean Anisson. The image depicts a curled up infant-like human, now referred to as a homunculus, inside the head of a sperm cell. This sketch is important to embryology because it is one of the most illustrative examples of preformationism, a theory of generation stating that each future member of any given species exists, fully formed though miniscule, within the gametic cells (sperm or eggs) of its parents. This theory was popular among naturalists in the eighteenth century.