Our technological preference for perfection can only lead us so far: as traditional transistor-based electronics rapidly approach the atomic scale, small amounts of disorder begin to have outsized negative effects. Surprisingly, one of the most promising pathways out of this conundrum may emerge from recent efforts to embrace defects to construct 'quantum machines.' Recently, individual defects in diamond have attracted interest as they possess an electronic spin state that can be employed as a solid state quantum bit at room temperature. We provide an overview of temporally- and spatially-resolved optoelectronic measurements used to generate, manipulate, and interrogate single electron and nuclear spin states on demand. The quantum engineering of spins and photons has enabled gigahertz coherent control, nanofabricated spin arrays, nuclear spin quantum memories, and nanoscale imaging for applications in science and technology.