The developing life, now called an embryo, is about the size of an apple seed (around 1 millimeter). A remarkable amount of development is happening in this tiny being! Major organ systems are beginning to form, including the brain, heart, skeleton, muscles, and other internal organs. This period, known as organogenesis, is a critical time for development. The chorionic villi, the early version of the placenta, and the umbilical cord are already establishing themselves and beginning to function, providing essential nutrients and oxygen to the rapidly growing embryo. The cluster of cells is taking on a more defined shape, resembling a tiny figure with the beginnings of a head, trunk, and even small bumps where the arms and legs will eventually develop. The nervous system, skeleton, muscles, and organs are all starting to form. The placenta, which will connect your circulatory system to your baby's, is developing, along with the amniotic sac, which will cushion and protect your baby throughout the pregnancy. The yolk sac, which initially provides nutrients, and the umbilical cord, which will become the lifeline between you and your baby, are also forming. Implantation, the process where the embryo embeds itself in the uterine lining, usually occurs between days 7 and 10 after fertilization. This is a crucial step for establishing the pregnancy.