<p>Sweat plays a central role in thermoregulation and offers a window into human physiology, yet real-time monitoring of the microscopic events that drive perspiration remains elusive. Existing wearable sweat sensors capture bulk sweat output but cannot resolve the rapid, gland-level secretory bursts that underlie electrodermal dynamics, particularly during motion-heavy activities. Here we present a wearable optical–electrical skin sensing platform that provides a direct in situ correlation between the fundamental metrics of sweat gland activity—the density of bursting glands, their burst frequency and the calculated burst volume—with simultaneously measured skin conductance and volumetric sweat rate, both at rest and during exercise. By synchronizing high-resolution microscopy, co-localized electrodes and microfluidic sensing, we show that skin conductance phasic spikes are precise electrical signatures of discrete glandular bursts, with both amplitude and frequency scaling linearly with bursting density and burst rate across rest and exercise. This integrated approach suggests a dual-mode perspiration control mechanism in which glands first increase burst frequency and then modulate burst volume to meet rising sweat demands, establishing a framework for real-time, gland-level sweat physiology monitoring.</p>