A human embryo is the early stage of human development that occurs after fertilization, when a sperm cell joins with an egg cell. This stage lasts from conception until about eight weeks into pregnancy. During this time, the embryo undergoes rapid cell division and begins to form the basic structures of the body, including organs and tissues. After eight weeks, the embryo is referred to as a fetus. The development process is crucial, as it lays the foundation for all future growth and development. Proper nutrition and a healthy environment are essential during this period to support the embryo's development.