Ah, the smell of coffee brewing, of tea steaming, hot chocolate beckoning on a cold winter’s day… the fizzy kick of Coca-Cola on a long journey. It’s wonderful, really. The taste, feel and cultural significance of each of these drinks may differ, but they all share one key ingredient: caffeine. Caffeine is the most commonly used mood-altering drug for humans: it wakes us up, prepares our minds for work, keeps us alert (we think) and provides a shared experience during informal interactions.