The term 'baby-to-be' refers to the stages of development that a baby goes through before birth. The first stage is the ZYGOTE, which is a single cell formed when an egg and sperm join together. This cell then divides and multiplies to form an EMBRYO, which is a group of cells that will eventually become the baby. Finally, the EMBRYO develops into a fetus, which is the stage of development that lasts from 8 weeks after conception until birth.