1st modern Air Conditioning system

Willis Carrier developed the first modern air conditioning system to solve humidity issues at a Brooklyn printing plant, improving print quality and production consistency. His system used cooling coils to reduce moisture, laying the foundation for the air conditioning industry. Carrier's innovation transformed movie theaters into cooling havens, was adopted in various businesses, and led to defining air conditioning's four core functions: controlling temperature, humidity, air circulation, and ventilation. 

Carrier later patented his invention and established the Carrier Engineering Corporation.