A transcutaneous electrical nerve stimulator (TENS) is a small, battery-operated device that sends electrical impulses through the skin to relieve pain. It works by reducing central excitability and restoring inhibition with repeated usage. Despite initial effectiveness, it may decrease in effectiveness after a few months. TENS is consistently more effective than placebo for pain relief and has been found to decrease postoperative pain. In this tutorial video, the science behind TENS therapy for pain is explored and discussed, including its role in reducing anxiety and heart rate.