This feature article reviews the authors' work combined with highlighted specific aspects of polyaniline (PANI) macro/nanostructures, focusing on such issues as the following. 1) The new development of a hard-template method. 2) Evaluation of a template-free method in universality, controllability, and simplicity as well as the self-assembly mechanism. 3) Multi-functionality based on a template-free method associated with other approaches. 4) Cooperation effect of a micelle soft-template and molecular interactions as a new tool to complex 3D microstructures assembled from 2D or 1D nanostructunes. 5) Electrical and transport properties of a single PANI nanotube, as measured by a four-probe method. 6) Sensors guided by reversible switching wettability through a doping/de-doping process. An outlook is also briefly given.