One drop of certified pure therapeutic grade essential oil contains approximately 40 million trillion molecules. We have 100 trillion cells in our bodies, and that's a lot! But one drop of essential oil contains enough molecules to cover every cell in our body with 40,000 molecules. Considering that it only takes one molecule of the right kind to open a receptor site and communicate with the DNA to alter cellular function, you can see why even inhaling a small amount of oil vapor can have profound effects on the body, brain and emotions.