Time Travel
This might be considered the most theoretical on our list, but nanotechnology is clearly a potential asset to time travel. It is very likely that any time machine or any form of travel in space that affects time will use nanotechnology in some way. Naturally, there is always a risk that if we are able to somehow break the known laws of physics and go back in time, one could see how harmful that could be. Meanwhile, we know the laws of physics allow us to travel into the future at a pace much faster than what we experience on Earth. This can only be done in space, considering it involves only “spacetime” and does not connect to the time of any planet. Thus, nanotech could potentially cause a person to go into the distant future yet be incapable of getting them back to their previous time.