Effective circuit design and debugging require developing an intimate understanding of the behaviors of a complex system. In my work, I’ve distilled barriers to such understanding to three fundamental challenges of circuit design: transparency, malleability, and modelability. In turn, my research contributes tools that address these challenges through novel changes to the circuit design workflow: Pinpoint improves transparency and malleability in the debugging of printed circuit boards (PCBs) by augmenting board connections with automatic instrumentation and reconfigurable connectivity. Scanalog similarly improves transparency and malleability in prototyping by providing an interactively reprogrammable platform on which to design and tune fully instrumented mixed-signal circuits. My ongoing work addresses issues in modelability through tools that generate empirically-derived fault models and highlight causal relationships between components in a circuit. By evaluating these interactions, my research examines the role of exploratory understanding in circuit design, asking, “How can tools promote understanding of a circuit by facilitating exploration and reflection?”