The transition metals are also referred to as the d block because their valence orbitals are the d shell (see illustration on this page). There are five different d orbitals. Three (d_xy, d_xz, and d_yz) of these five look similar, just with different orientations in space. The fourth (d_x²-_y²) has the same shape as the previous three, but the loops point in along the axes as opposed to between them. Finally the d_z² looks like a p-orbital pointed along the z-axis with a ring (technically a torus) around it.