Clinical physiology is an academic discipline and a medical specialty for physicians primarily in Sweden, Denmark, Finland, and Portugal, dedicated to diagnosing diseases by assessing organ functions. Founded by Professor Torgny Sjöstrand in Sweden, this specialty uses a functional approach to understand pathophysiology, employing various advanced tests. These diagnostic methods include evaluating electrical activity (e.g., electrocardiogram), airflow (spirometry), blood pressure, and utilizing imaging techniques like ultrasound, MRI, and PET to measure movements, velocities, and metabolic processes of organs such as the heart, lungs, and kidneys. While a physician specialty in some countries, in others like the UK and Australia, it is practiced by non-medical allied health professionals, underscoring its critical role in providing precise functional diagnoses globally.