Material formation mechanisms and their selective realization must be well understood for the development of new materials for advanced technologies. Since nanomaterials demonstrate higher specific surface energies compared to their corresponding bulk materials, the homoepitaxial growth of nanomaterials on bulk materials is not thermodynamically favorable. We observed the homoepitaxial growth of nanowires with constant outer diameters on bulk materials in two different, solution-based growth systems. We also suggested potential mechanisms of the spontaneous and homoepitaxial growth of the ZnO nanostructures based on the characterization results. The first key factor for favorable growth was the crystal facet stabilization effect of capping agents during the early stages of growth. The second factor was the change in the dominant growth mode during the reaction in a closed system. The spontaneous, homoepitaxial growth of nanomaterials enables the realization of unprecedented, complex, hierarchical, single-crystalline structures required for future technologies. (C) 2020 Elsevier Inc. All rights reserved.