Definition: The word "free radicals" refers to molecules that are unstable but not broken down into smaller components by normal cellular processes, which can lead to oxidative stress or damage. These free radicals are also known as reactive oxygen species (ROS) because they can produce radicals like hydroxyl radical and singe oxygen in the cell's structure. Antioxidants are substances that help neutralize free radicals to prevent them from damaging cells and tissues. They also play a key role in maintaining cellular homeostasis by helping to prevent oxidative stress, such as through their antioxidant properties. In the context of disease and health, antioxidants act to protect cells against damage caused by free radicals. This can involve several different types of antioxidants including flavonoids, vitamins, and minerals that help to neutralize free radical formation in various cells and tissues within the body. The term "PMC" stands for "Patient-Made Compounds." These are substances made specifically with the goal of improving health outcomes through their ability to protect or repair cellular structures. In other words, they act as a "patient-made" therapy that can be administered by patients themselves, without having to undergo invasive medical procedures. By understanding the concept of free radicals and antioxidant systems in disease and health, it is possible to develop more effective treatments and therapies for various diseases such as cancer, cardiovascular disorders, diabetes, and others.