Reading
I love reading. Being so ubiquitous, we take it for granted how useful it is. For English, all we need is less than 40 distinct written symbols for us to convey practically every thought imaginable. We can express our thoughts and feelings, communicate events, describe how our world works just with abstract symbols. Even with all stuff mankind has created, the written language is still one of its top inventions; without it most other great inventions aren't possible.All this shit should be obvious to anyone reading it, but it's worth repeating.