HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the compound into a topological insulator. The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures exhibit the quantum spin Hall effect, where a pair of spin polarized helical edge channels develops when the bulk of the material is insulating. Our transport data[1-3] provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topological insulator. To turn the material into a 3-dimensional topological insulator, we utilize growth induced strain in relatively thick (ca. 100 nm) HgTe epitaxial layers. The high electronic quality of such layers allows a direct observation of the quantum Hall effect of the 2-dimensional topological surface states[4]. These states appear to be decoupled from the bulk. This allows us to induce a supercurrent is induced in the surface states by contacting these structures with Nb electrodes[5]. [1] M. König et al., Science 318, 766 (2007). [2] A. Roth et al., Science 325, 294 (2009). [3] C. Brüne et al., Nature Physics 8, 486 (2012). [4] C. Brüne et al., Phys. Rev. Lett. 106, 126803 (2011). [5] L. Maier et al, Phys. Rev. Lett. 109, 186806 (2012); J.B. Oostinga et al., PRX 3, 021007 (2013).