Embryology is the branch of biology that studies the formation, development, and growth of embryos in animals and plants. It focuses on the processes that occur from the fertilization of an egg to the development of a fully formed organism. Key areas in embryology include:

1. Fertilization: The fusion of male and female gametes (sperm and egg) to form a zygote, marking the beginning of a new organism.

2. Cleavage and Blastulation: Rapid cell division following fertilization, resulting in a cluster of cells called a blastula.

3. Gastrulation: The process where cells begin to differentiate and organize into distinct layers: ectoderm, mesoderm, and endoderm, which will form all the tissues and organs of the organism.

4. Organogenesis: The formation of organs and structures from the three germ layers, with specific tissues and organ systems developing at different rates and in specific sequences.

5. Morphogenesis and Growth: Changes in the shape and form of the embryo, influenced by genetic and environmental factors, which leads to the final structure of the organism.

Embryology is crucial for understanding congenital diseases, developmental biology, and evolutionary processes, as well as applications in regenerative medicine and genetic engineering.