Our mornings never really feel like they have begun until we have that first cup of coffee.

It's almost like it has magical powers (or that's how it feels, anyways). But we've never actually thought about what that morning cup of coffee actually does for us - like, does it actually work? Or is it simply all in our heads? According to MentalFloss, coffee may not actually quite have the all-powerful, morning boost we're after - at least, not in the way we think. And the reason why all begins with a bit of biology. Throughout the day, a neurochemical called adenosine is created in your body - and your nervous system uses special receptors to monitor the adenosine levels in your body. As the day continues, more and more of the neurochemical passes through the receptors - and, eventually, it makes you sleepy (and that's also the reason you get tired at night). Since caffeine is the same size and shape as adenosine, the adenosine receptors can't tell the difference - and caffeine is able to attach to the A1 receptor. And that, in turn, makes it more difficult for a lot of you body's adenosine molecules to enter - which means that the caffeine is keeping you from getting tired. Here's where that oh-so-relied-upon coffee boost kicks in. Since the adenosine receptor is clogged, other neurotransmitters - like dopamine and glutamate - are able to get a bit of a head start. When your dopamine levels swell, your mind gets a huge boost of energy - and there's your coffee boost. However, while caffeine can make you feel on top of the world, it can also make you crash. Hard. It takes a good few cups of coffee - around four - to even block half of the A1 receptors in the brain. Throughout this, the adenosine continues to build in your body - but it has nowhere to go. Which is why when the caffeine wears off finally, and all the extra adenosine moves through your receptors, it can make you feel even groggier than before.