Germ Theory is the scientific concept that microorganisms, or germs, are the primary cause of many diseases. This theory was developed in the 19th century, with significant contributions from scientists like Louis Pasteur and Robert Koch. They demonstrated that specific germs could lead to specific illnesses, changing how we understand and treat diseases. Before Germ Theory, many believed that diseases were caused by miasmas or "bad air." The acceptance of Germ Theory led to improved hygiene practices, vaccinations, and antibiotics, significantly reducing the spread of infectious diseases and improving public health worldwide.