Caffeine has the unique ability to fit into receptor sites in your body for adenosine because it’s so structurally similar to the real thing. Normally, when your receptor sites are filled with real adenosine, your body shifts into rest mode. The issue with caffeine going into those receptors is that it simply sits there like a distant relative overextending their stay on your couch. It doesn’t actually turn on functions, like adenosine would, to make you tired. As a result, your brain and body are still trucking along and you don’t realize that you’re actually sleepy.
