All the peppers, from the sweet bell peppers to the hottest chili, now the Nāga chilli, belong to the Solanaceae family. This family includes potatoes, eggplants, tobacco and another common plant from the New World, the tomato. The spice of the chilies comes from a chemical, capsaicin, which produces the burning sensation in our mouth. The Scoville Heat Unit Scale (SHU) is a way to measure the level of hotness of the chilies, or the concentration of capsaicin in the chili. The scale is divided into multiples of 100, and goes up to 16,000,000,000. To put it into something meaningful, jalapenoes are in a range between 2,500-5,000 SHU.
Capsaicin does not dissolve in water. So because it doesn’t dissolve in water, you cannot eliminate the burning sensation of the chili by drinking water, but drinking something rich in fat, such as milk, does help with this situation.
Chilies are also an extraordinary condiment. They have a high nutritive value, rich in vitamins (specially C and A), and are the vegetable with the highest concentration of ascorbic acid.