Flower-like CuO nanostructures were fabricated to enhance nucleate pool boiling. These nanostructures enhance boiling due to capillary wicking induced by their high surface area-to-volume ratio. Despite only having a thickness of 3-4 mu m, similar to 58% improvement in critical heat flux (CHF) was obtained by the addition of CuO nanostructures to both a smooth surface and a microgrooved surface. Because the CuO nanostructures are processed at room temperature, they can be easily combined with microfabricated cavities for additional boiling enhancement. Supplemental files are available for this article. Go to the publisher's online edition of Nanoscale and Microscale Thermophysical Engineering to view the free supplemental file.