1 - morula, 2 - blastula 1 - blastula, 2 - gastrula with blastopore; orange - ectoderm, red - endoderm<unk>  (from Greek ἔμβρυον,<unk> ryon, "the unborn,<unk> ryo"; and -λογία, -logia) is the branch of biology that studies the prenatal development of gametes (sex cells), fertilization, and development of<unk> ryos and fetuses. Additionally,<unk>  encompasses the study of congenital disorders that occur before birth, known as teratology. Early<unk>  was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, epigenesis. Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern<unk>  developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance.
Embryology
Reproductive immunology
Obstetrics
Reproductive technology
Maternal–fetal medicine
Teratology
Sexology
Reproductive medicine