"We present a set of case studies in which students create, customize, and personalize their own scientific instruments-and thus become engaged in scientific inquiry not only through observing and measuring but also through designing and building. Although computational technologies have, in general, contributed to making today's scientific instruments more "opaque" (that is, less understandable) and less aesthetically pleasing than their predecessors, we argue that these same technologies can be used to bring back a sense of transparency and aesthetics to the design of scientific instruments. We analyze how students, by building their own scientific instruments, can pursue a broader range of scientific investigations of their own choosing, feel a stronger sense of personal investment in their scientific investigations, and develop deeper critical capacities in evaluating scientific measurements and knowledge."