Years ago, when I connected all the dots, I realized that life is a chemical reaction that has some control over its rate of reaction. Unlike a match that burns furiously as long as there is enough fuel, living organisms do a controlled burn.

Of course, all matter in the universe is chemical so when chemists hear the term ‘natural' to refer to substances that come from living organisms - like plant extracts, for instance - they pucker their lips up in a ‘we know better than that' smile while issuing cautions. Plant extracts can be deadly at a very low concentration. Botulism is a poison excreted by an anaerobic organism. Poison ivy, stinging nettles, even otherwise-harmless mushrooms grown in toxic soil become toxic.

Atoms of sodium are a nasty substance. Expose sodium to the air and it will burn. Chloride also is deadly. Let the two react to each other and you end up with salt - which is necessary for your survival.

Oxygen is also deadly and natural. An important evolutionary change was needed before life on earth could survive in an oxygen atmosphere. Most living organisms have found a way to protect themselves from oxygen, but there are some exceptions. In every inch of soil lives millions of organisms that die when exposed to air we breath.

It's easy to complicate any conversation about chemicals, but the basics are simple; electrons and protons react to each other to make every substance in the universe. Chemical reactions make the stars shine and rivers run. By the way, those reactions also take place in your brain to form thoughts, memories, and emotions.