Steinitz's Theorem (proved in 1922) is one of the oldest and most prominent results in polytope theory. It gives a completely combinatorial characterization of the face lattices of 3-dimensional polytopes. Steinitz observed that the technique of proving his theorem also implies that for any 3-dimensional polytope the set of all its realizations is a trivial topological set. In other words: realization spaces of 3-dimensional polytopes are contractible.