Define embryogenesis.

Hint:
 Sexual reproduction involves a number of procedures which are termed as pre-fertilization events, fusion of gametes, and post fertilization events. Embryogenesis is one of the post fertilization events. It is the process of development of an embryo which is the resultant structure of fertilization after the formation of zygote. This is a very complex procedure.

Complete answer:
Embryogenesis- Embryogenesis is the process of development of the foetus from the zygote. It is also known as embryonic development. It starts with the fertilization of an egg (ovum) by a sperm cell (spermatozoon). This results in the formation of zygote. Then the zygote undergoes a series of mitotic divisions leading to the formation of an embryo.
Human development: It is a highly detailed and compound process, in which a single cell differentiates and develops into a multicellular human being. A continuous process in which there is the fertilization of an egg (ovum) by a sperm cell (spermatozoon) form a zygote which divides and differentiates into a definitive organ system and thereafter into their early functional stage.
Duration and the pregnancy stages-The gestation period of humans are about 266 days (38 weeks, 9 months). There are three stages of pregnancy-
The first trimester which covers the 1st week to 14th week
The second trimester covers the week 15-26
The third trimester covers week 27-40.

Note: The stages of mitotic divisions of a zygote is as follows
zygote-morula-blastula- gastrula
Gestation period: The period during which embryo and foetus are contained in the uterus.
Embryology- Embryology is the scientific study of embryos. It deals with the ontogenic development of organisms. It is the process of the development from the single cell, embryo to a baby. Embryology also refers to prenatal development of the foetus. Karl Ernst von Baer is called the Father of Embryology.