The process of an egg turning into a baby begins with fertilization. During sexual intercourse, sperm travels to the fallopian tube, where it may encounter and penetrate the egg, resulting in fertilization. The fertilized egg, now called a zygote, starts dividing rapidly as it travels down the fallopian tube towards the uterus. Once in the uterus, it implants into the uterine lining and continues dividing, forming a ball of cells known as an embryo. Over the next weeks and months, the embryo develops into a fetus, growing and developing vital organs and body systems. After about 40 weeks of gestation, the fetus is fully developed and ready for birth, resulting in the birth of a baby.