The chromosomes from the sperm and egg joined over 24 hours ago. It takes around 30 hours for the resulting zygote to complete its first cell division. The zygote, at only 0.1 mm in diameter goes on to divide into 16 cells, forming a compact ball.
Cell division is such that the ball of cells is hardly any larger than the original zygote. The ball of 16 cells, now known as a "morula" (as it resembles a mulberry), travels toward the uterus, entering on day three after fertilization. Every cell within the morula is totipotent, meaning it is able to form any type of cell. From this point onward the cells will lose this function as they start to specialize.