SHU		Pepper
0-100		Bell
500-1000		New Mexican
1000-2500		Ancho, Pasilla
2500-5000		Jalapeno
5,000-15,000		Serrano
15,000-30,000		de Arbol
30,000-50,000		Cayenne & Tabasco
50,000-100,000		Chiltepin
100,000-350,000		Scotch Bonnet and Thai
200,000-577,000		Habanero
16 million		Pure Capsaicin

How is the heat in Peppers measured?
In 1912, Wilbur Scoville, a chemist, developed a unit to measure the head in chile peppers that is still used today, the Scoville Heat Unit. His original test was a taste test where ground chile peppers are diluted in sugar water and tasted. More sugar is added until the heat can't be tasted. According to the Guinness Book of World Records, the Red Savina Habanero is the hottest pepper on Earth with a rating of 570,000 SHU.

What makes the pepper hot?
Capsaicin, a crystalline alkaloid is produced by the pepper and is responsible of the heat. Capsaicin is incredibly powerful and seemingly unaffected by heat or cold so it stays potent despite cooking or freezing. Because it is colorless and odorless, it can only be measured in a laboratory.