Over the centuries, caffeine has been identified in more than a hundred plants but the most common sources are coffee, C. sinensis teas, maté, cocoa products, cola beverages, energetic beverages and different types of pharmaceutical drugs. Currently, approximately 80% of the world's population consumes a caffeinated product every day. The safety aspects of caffeine have been extensively studied in numerous animal species and in humans. These and other related aspects are discussed in this chapter.