René Laennec invented the stethoscope because he felt uncomfortable placing his ear directly on a female patient's chest to listen to her heart (the standard method at the time). He rolled up a piece of paper into a tube and found it amplified the sound while maintaining distance. He later developed a wooden version. The stethoscope allowed doctors to diagnose heart and lung conditions (like pneumonia and tuberculosis) with much higher accuracy. This invention marked the beginning of modern clinical diagnosis, where physicians look for physical signs within the body rather than relying solely on the patient's description of symptoms. It remains the most iconic symbol of the medical profession worldwide.