In this talk I will survey progress during the last couple of years in the controlled growth of epitaxially nucleated nanowire structures, obtained via local catalytic activation of growth. From an application point of view, progress in the technologies which allow control of geometrical dimensions and positioning of nanowire structures and devices is of great importance, as is the recently demonstrated ideal formation of III-V nanowires epitaxially grown on silicon substrates. From the perspective of designing and realizing complex device structures, by which quantum phenomena can be utilized, the formation of axial as well as radial heterostructures within a nanowire is of special interest and I will give different examples of how this has been achieved. Finally, I will present a couple of quantum device families that we have been working on in the last year, such as wrap-gate field-effect transistors and multiple-barrier storage devices.