Most baking includes eggs, and any time you're working with eggs is a great time to throw in a little biology. You can talk about the parts of the egg and how there's no baby chick in this one. You can talk about bacteria. Bacteria have their own kingdom along with Animals, Plants, Fungi Protisits and Archbacteria. Bacteria are not invisible, but they are tiny!
The bacteria found in eggs is called salmonella , and makes us very sick if it gets into our bodies. That's why we always wash our hands with hot water after we touch the cookie dough. However, the heat that changes the cookie dough into cookies (chemical change), also kills the bacteria. That's why cookies are not only yummy, but safe to eat.