As you stay awake, adenosine builds up to signal tiredness. Caffeine's molecular structure is similar enough to plug these receptors without actually activating them.

Caffeine acts as a natural neurotoxin to paralyze bugs that eat the leaves, though trace amounts in the plant's nectar actually help honeybees remember the flowers.

Highly pressurized carbon dioxide acts as both a liquid and a gas. It effectively penetrates unroasted coffee beans to dissolve the caffeine without leaving toxic residues.

While caffeine is a mild diuretic that increases urination, the large amount of water in brewed coffee or tea easily offsets any fluid lost.