After the first day, biological development into human form progresses very rapidly.
Two weeks after conception, the embryo has a developing brain and rudimentary heart.
Three weeks after conception, the baby has a working heart, the beginning of vertebrea, a closed circulatory system separate from the mother's, developing eyes and ears and the beginning of lungs.
Around the 25th day, lungs are fully developed, and the heart begins to beat. The heart circulates blood throughout the fetus' body; blood completely different and often incompatible with that of the mother.
The baby's developed systems are already separate from those of the mother; one month after conception it is no longer a part of her.
Five weeks after conception, the embryo has developed smaller organs such as a bony jaw, and by six weeks, it has fully developed a vertebral column , ribs, a four-chambered heart, fingers, and nostrils. The baby also has a developing nervous system, and brainwaves are recorded at an average of 40 days after conception. Death is often defined as the cessation of brainwaves, and it follows that the presence of these brainwaves guarantees the individual life of the fetus.
By seven weeks, the baby has developed a pancreas, a bladder, kidneys, a tongue, and a larynx, and muscles begin to appear.
By eight weeks, the embryo has ears, fingers, and toes, and all key bodyparts are developed or developing.
Nine weeks into the pregnancy (about 2 months), the baby can feel pain.
In ten weeks, the baby has developing fingernails, and also begins to move by itself.
By eleven weeks the baby has the fingerprints that will identify it for the rest of its life.
Twelve weeks after conception, the baby's gender can easily be determined, it is able to swallow, and its kidneys are able to make urine.
Fourteen weeks into pregnancy, the fetus has fully developed legs. It can kick, sleep, and move its head.