Or there's the classic sci-fi book Flatland, which asks: what would it be like if we lived in two dimensions? As if we lived in a piece of paper, or only on the surface of a table? 
The notion of up and down would be meaningless; we’d only have left and right, and front and back. So we’d be moving in two dimensions rather than three, and we’d also perceive everything around us to have only two dimensions.
There wouldn’t be any going over a fence, or peeking under a door. If a thing blocked your way, it would block it completely, and everything behind it would be completely invisible.
Of course, you wouldn’t be able to pass through things in Flatland, the same way you can’t in the real world. So if a Flatlander stopped directly in front of you, you’d have to pass to either side, or not at all.
Life in Flatland may seem like an academic abstraction. But actually, while our world is three-dimensional, there are some things in it which effectively have only two dimensions, especially in the world of #nanoscience.
Wonder material graphene is effectively two-dimensional, it's only one atom thick! So electrons in graphene are effectively in 2D, Flatland, and can’t use the third dimension to go around each other.
You can read lots more about graphene here if you want more detail: en.wikipedia.org/wiki/Graphene or go ask @ambercentre who have a lot of researchers working on it!
