What happens during the embryonic stage?

Human development begins at conception. The first two weeks are called the germinal stage. This period is marked by rapid cell division (mitosis) and uterine implantation. In human embryology, the term embryo refers to an unborn child in its development between the third and the eighth week after fertilization (10th week of pregnancy). Initial sensory perceptions, learning processes, and organ formation take place during the embryonic phase. The complex cardiovascular and nervous system formation occurs between the 3rd and 4th week after conception. The brain begins to develop during the 5th and 6th week. On the 40th day post-conception, both hemispheres of the brain are recognizable, and from the 44th day, electrical brain activity is detectable. By the end of the 6th week, the spinal cord is formed, impulses from the brain can be processed, and neural pathways begin to connect. At eight weeks, all organs are formed and only need to grow and mature. The preborn baby, measuring 3cm, then enters the fetal stage, lasting from nine weeks until birth.
 

Source: https://www.profemina.org/de-it/abtreibung/faq/hat-der-embryo-das-kind-schmerzen-bei-der-abtreibung