Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Although oxidation reactions are crucial for life, they can also be damaging, as they can produce free radicals - atoms, molecules, or ions with unpaired electrons or an open shell configuration that can start chain reactions, which can cause damage to cells or even kill them. Antioxidants - molecules capable of inhibiting the oxidation of other molecules, terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions. Learn more about antioxidants, their classification and their role in the complex biochemistry that keeps us alive in the following pages.