In 1912, pharmacist Wilbur Scoville developed a method to measure the heat of chili peppers. His original test, the 'Scoville Organoleptic Test,' involved diluting a pepper extract in sugar water until the heat was no longer detectable by a panel of human tasters. For example, a pepper with a rating of 5,000 Scoville Heat Units (SHU) had to be diluted 5,000 times. The burning sensation of chilis is caused by 'capsaicin,' a chemical compound that tricks the body's pain receptors (specifically TRPV1) into feeling heat, even though there is no physical burn. Today, High-Performance Liquid Chromatography (HPLC) is used for more objective measurements. While a bell pepper is 0 SHU, the world's hottest peppers, like the Carolina Reaper, can exceed 2,000,000 SHU.