This false-coloured scanning electron micrograph shows caffeine crystals. Caffeine is a bitter, crystalline xanthine alkaloid that acts as a stimulant drug. In plants, caffeine functions as a defence mechanism. Found in varying quantities in the seeds, leaves and fruit of some plants, caffeine acts as a natural pesticide that paralyses and kills certain insects feeding on the plant. (via Wellcome Image Awards 2012 | Wellcome Image Awards)

This false-coloured scanning electron micrograph shows caffeine crystals. Caffeine is a bitter, crystalline xanthine alkaloid that acts as a stimulant drug. In plants, caffeine functions as a defence mechanism. Found in varying quantities in the seeds, leaves and fruit of some plants, caffeine acts as a natural pesticide that paralyses and kills certain insects feeding on the plant. (via Wellcome Image Awards 2012 | Wellcome Image Awards)

"The general consensus on caffeine studies shows that it can enhance work output, but mainly in certain types of work. For tired people who are doing work that’s relatively straightforward, that doesn’t require lots of subtle or abstract thinking, coffee has been shown to help increase output and quality. Caffeine has also been seen to improve memory creation and retention when it comes to “declarative memory,” the kind students use to remember lists or answers to exam questions."

What Caffeine Actually Does to Your Brain