Babies are formed when the sperm cell from the male testicular gonad meets with the women's egg cell (from the ovaries). This penetration causes the<em> "fertilization process." </em>This naturally occurs two weeks from the woman's last day of menstruation. The fertilization allows the egg to rapidly divide. This is followed by "implantation," a process whereby the blastocyte attaches to the woman's endometrium. <u>Around three weeks, the blastocyte is formed into an embryo. </u>This will be called fetus once the woman reaches its 8th week of pregnancy.
This is a brief process regarding your question on how babies are formed.