Transcranial magnetic stimulation combined with electroencephalography (TMS–EEG) offers a unique opportunity to investigate human thalamocortical circuits non-invasively from a causal perspective. Delivering a controlled perturbation—the TMS pulse—to a targeted cortical region and recording the ensuing TMS-evoked potentials (TEPs) reveals physiological features that complement those accessible through observation alone, such as through the resting EEG. These features include cortical excitability, effective connectivity, oscillatory dynamics, and recurrent interactions across cortical and thalamocortical circuits. Methodological advances—ranging from TMS-compatible EEG equipment to biological artefact-control procedures—now allow researchers to isolate genuine neural responses from stimulation-related confounds with increasing reliability. These insights are turning TMS–EEG into a versatile tool for basic and clinical neuroscience, enabling the characterization of circuit-level mechanisms across behavioral states, from wakefulness and sleep to anesthesia and disorders of consciousness, as well as fostering the development of biomarkers relevant for stroke, psychiatric disorders, neurodegeneration, and recovery of function. This chapter provides an overview of the instrumentation, experimental procedures, physiological principles, and representative applications of TMS–EEG, highlighting both its strengths and limitations. We argue that TMS–EEG holds substantial promise for advancing mechanistic models of thalamocortical function in humans and for developing clinically meaningful biomarkers.