Suppose f is a homeomorphism between R2 and R3. Take the compactification of the domain and the range to get S2 and S3 respectively. Let f map ω to ω. Verify that f is still a homeomorphism. Now the two spheres are homeomorphic. This has been ruled out by the previous theorem. Therefore each euclidean space Rn is distinct.
Since Rn maps homeomorphically onto the interior of Dn, open balls of different dimensions are also topologically distinct.