There's no doubt about it, drinking a coffee or any caffeinated drink when you feel tired will make you feel more alert but let's take a second to think about what coffee is.

　　我们都知道，当你感到疲倦时，喝杯咖啡或任何含有咖啡因的饮料，你会清醒许多，不过让我们来想一想咖啡到底是何方神圣。