Scientists have created embryos. What does that mean? And what comes next? Save Normal text size Advertisement Every cell in your body comes from a single cell: an egg, fertilised by a sperm. Each contains the exact same genetic blueprint for your life: your DNA. Yet cells in your brain look and behave nothing like those in your muscle or skin. Professor Jose Polo in front of images of his model embryos. Credit:Monash University Why? Because while each cell has the same instructions, each cell only reads certain sections â certain genes. A layer of what are called epigenetic instructions sit on top of your DNA, telling each cell which parts to read and which parts to ignore.