Fertilization is actually a very complicated process there are many biologists who have spent their whole lives trying to understand the steps involved in fertilization! The process also varies in different living things; for example, plants do it a bit differently than humans. Even in the animal world, there is lots of variation for instance, some animals do it outside of the body while others do it inside (like us). For the sake of explanation, lets talk right now about fertilization in humans. Basically, fertilization occurs when a sperm (from a male) and an egg (from a female) join together to make a new living thing, a baby.

When Fertilization Occurs:
First, the sperm has to find the egg. Many eggs have been shown to release chemicals into the surrounding area to help the sperm sense it and swim in the right direction. In humans, the egg is typically sitting in the fallopian tube in the womans body at this point. Once the sperm finds the egg it attaches to the outside of the egg and burrows through the top layers to get to the inside. This causes a big reaction in the egg, which quickly forms a wall around it so that no more sperm can come in. The one sperm that is inside this wall then connects to the egg cell and transfers the DNA it holds inside, and the female and male DNA combine together. The cell is now called a zygote. The zygote starts to divide into many copies, and it floats down the fallopian tube into the uterus - it attaches to the wall of the uterus and stays there, getting nourishment from the wall where it is connected to the mother until the baby is born.