A new set of branched nanowire or nanotree structures and their fabrication process. Some structures have one or more of the following distinctions from other branched nanowires: (1) the trunk and branch diameter and branching number density can be changed along the trunk's length; (2) the branch's azimuthal direction can be controlled along the trunk's length; (3) the branch's diameter can be modulated along its length; (4) the crystal orientation and branches of the ensemble of nanowires can be aligned on a non-epitaxially matched substrate. The structures are made by a geometrically controlled kinetic growth method.