Drawing from core disciplines of inorganic, organic, and biological chemistry, Prof. Chang's laboratory pursues new concepts in sensing and catalysis to study metals in biology and energy. They have developed activity-based sensing (ABS) as a general technology platform to enable biological applications that include imaging and diagnostics, proteomics, and drug delivery. These molecular probes have identified copper and hydrogen peroxide as signals for regulating processes spanning neural activity and neurogenesis to fat metabolism, opening a field of transition metal signaling. Their efforts have advanced artificial photosynthesis through the development of molecular catalysts that mimic enzyme biocatalysts or heterogeneous materials catalysts, as well as hybrid bioinorganic, organometallic, and supramolecular systems that merge molecules with biological and/or materials components. Representative project areas are transition metal signaling, activity-based sensing, metals in neurobiology, artificial photosynthesis.