One of the more interesting and fundamental concepts to grasp in physics is that of the observer and his or her effects on an environment.
The way we view the world on a moment by moment basis makes it seem like we can sit behind a plexiglass shield and watch things happen. But in quantum physics, this is not the case. And it’s not because we lack the technology to observe without interacting, it’s a principle that is inherent within the system itself.
Another corollary is that of the measurement of momentum (mass x velocity) and measurement of position. The more precise you get on one (momentum or position), the less precise you can be about the other. Again, this is not due to lack of technology. It’s inherent in the principles of the system.
These are pieces of the puzzle I find mind boggling and if you do too, I encourage you to read up and try to mess with your view of reality :p
The Tao of Physics (an awesome overview of quantum physics and its relations to eastern ways of thought)