Caffeine is the most widely consumed stimulant in the world. It works by blocking adenosine receptors in the brain to make people feel more alert and by increasing the release of adrenaline and dopamine to boost wakefulness, physical energy, and feelings of pleasure. However, caffeine also prevents people from getting deep, restorative sleep by interfering with adenosine receptors which are important for sleep. While a moderate amount of caffeine has some health benefits, consuming too much caffeine, especially late in the day, can negatively impact sleep quality and lead to health issues over time due to sleep deficits accumulating. Moderation of caffeine intake is recommended.