The 2025 Nobel Prize in Physiology or Medicine has been awarded to Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for their groundbreaking discoveries on regulatory T cells (Tregs). These cells play a critical role in peripheral immune tolerance, preventing autoimmune attacks and maintaining immune system balance. Sakaguchi's seminal 1995 research first identified this T cell subset, while Brunkow and Ramsdell's subsequent work further elucidated their molecular mechanisms. Their work has catalyzed the development of new therapeutic strategies for autoimmune diseases, cancer, and transplant medicine.