A tissue system includes: a support material; and a vascular network comprising a plurality of channels disposed in the support material. A method includes printing a bioink in a support structure to form a network of vascular precursor materials; and converting the vascular precursor materials into a physiologically relevant vascular network. Notably, the tissue systems, networks, etc. are physiologically-relevant, i.e. exhibiting one or more characteristics indicative of physiological relevance, such as a substantially fractal geometry, inter-vessel spacing, cellular composition, dermal structure, concentric multi-layered structure, etc.
 The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.