It took me some time to realize that plants actually convert gas into leaves and stems. You see, carbon dioxide is made of 1 atom of carbon and 2 atoms of oxygen. We all know that the oxygen is given out into the air but what of the carbon? Well, it becomes a part of the plant. After all, plants are carbon-based beings... and so are humans. Except that we don't invent ourselves out of thin air. Plants do. So, I realised that every new leaf that sprouts on my plants means just that much less carbon in the air.
Maybe others are already aware of this but for me, it was a moment of epiphany.