How Do We Make Space 3 D?

We take it for granted we live in the three-dimensional space, but we do not perceive the three dimensions directly. Why do we consider the space to be 3D?
Are All Fractals Complex Systems?

Although almost all books concerning complex systems mention chaos and fractals, I suspect that not all fractals are complex systems.I have already explained chaos and complex systems. So, first I must explain what fractals are.