In nature, caffeine can be found from approximately 60 plant. Probably most commonly known source of caffeine is coffee bean. Other sources are for example tea leafs, cacao beans and chocolate. In addition, cola and energy drinks contain caffeine.
Some people fell that caffeine stimulates, energizes and can even help to concentrate. However, it might take three to seven hours for the body to halve the amount of caffeine, which means it is better not consume caffeine too late in the day or it might ruin good night sleep.