The word breath most often refers to the air we pull in to and pump out of our lungs (or to the action of doing so) as in “Take a deep breath.” But we also give the same word loftier qualities in phrases such as “the breath of life” and in practices like yoga that view the breath as a source of health and peace. Other traditions and languages also have words for breath in both these ordinary and spiritual senses, such as Latin spiritus, Hebrew ruach, and Chinese qi.

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But what about the breathing body itself? Unless we are wheezing or short of breath, we usually take the smooth coordination of our lungs, diaphragm, membranes, and blood cells as unremarkable. But let’s refocus our wonderment for a moment. The air is, when you come down to it, just a mix of gasses, but our body’s ingenious respiration of those gasses is a process to appreciate.

We breathe in air because it contains one gas that we must have: oxygen. We know that. Less familiar, though, is the step-down system that has evolved to make the most of the fact that, like all gasses, oxygen spreads out from wherever there is more of it to where there is less of it. Thanks to this step-down dispersal and our flowing  blood, we move oxygen from the air outside of us to every cell that is waiting for it, all several trillion—that’s several 000,000,000,000—of them.

Why oxygen? Its electrons are arranged in such a way that it interacts eagerly and often with other elements. It’s a potent extrovert. The body’s cells may get their nourishment from food molecules but not unless they also have oxygen handy to break those molecules down, which would be like our eating dinner without any acid in our stomach to digest it. No nourishment. Without oxygen, cells go hungry.

But a little oxygen goes a long way. The numbers surprised me. Only about twenty percent of the air that we breathe is oxygen. The rest is nitrogen and a percent or two of other gasses. And of that twenty percent of oxygen that we inhale, we actually use only about a quarter of it. The rest goes out again. Our inhalation is twenty percent oxygen; we exhale fifteen percent.

Once it is in our lungs, oxygen must get across the lung’s membrane to the blood stream that will move it around the body. As always, it moves to where there is less of it, so it steps down across the thin membrane to the empty hemoglobin molecules in the blood cells for the ride to the rest of the body.

As this convoy of oxygenated blood flows near, say, a finger, the oxygen detaches from the hemoglobin, steps down yet again across a membrane to a cell itself, and goes to work on the food particles. In the process, extrovert that it is, oxygen combines to form unusable carbon dioxide, which crosses the cell membrane back out to some empty passing hemoglobin that just dropped off oxygen elsewhere, rides the vein back to the lungs, gets off again, and is exhaled back to the air. Like riding the bus that you took to work in the morning back home at the end of the day.

I argue for the wonderment of a distribution system that pulls in air-borne oxygen in an endless rhythm, arranges for it to disperse itself across strategic membranes, loads it on to the blood for transport to a million million cells that it will help nourish, after which it returns the way it came in. Our stunning respiration makes oxygen look good—even divine.