Chillies spice up meals, adding a kick that not everyone can handle. There are many varieties of chilli peppers, ranging from mind-numbingly spicy to mild. Considering how important chillies are to certain cuisines and cultures, it comes as no surprise that there's a system that can measure the heat of different chillies. This measuring system is called the Scoville scale.

The Scoville scale was invented by a pharmacologist named Wilbur Scoville to measure the pungency and heat of chilli peppers, based on their capsaicin content. Initially, Wilbur Scoville ground up peppers and mixed them with sugary water. He had them tested by a panel of tasters who sipped on these solutions of sugar, water and pepper. The solutions were diluted bit by bit until they no longer scalded the tongues of the tasters. After this, a number was assigned to each chilli pepper based on the number of dilutions needed to kill the spiciness.

The measurements on the Scoville scale are divided into multiples of 100. One part per 1,000,000 dilutions of water is rated at 1.5 Scoville Units. Pure capsaicin, the component that makes chillies spicy, is rated between 15-16,000,000 Scoville heat units. The Scoville scale may be used to measure not just chilli peppers, but anything that is made from them, like hot sauce. In actuality, the concentration of capsaicin is measured.

Here is a look at some of the world’s hottest chillies:

Carolina reaper

Carolina reaper is officially the hottest chilli in the world. It has been estimated to have an average of 1,641,000 Scoville heat units. It has a shrivelled appearance and is considered 200x hotter than a jalapeno.

Trinidad moruga scorpion

It’s safe to say that any food item with ‘scorpion’ in its name isn’t for the faint-hearted. At 2,009,231 Scoville heat units, it has won the title of the second hottest chilli pepper in the world.

Trinidad scorpion butch T

The Trinidad scorpion butch T from Australia has formerly been on a Guinness World Record Holder (in 2011). While there are chillies that are hotter, this one is insanely hot too. Its name comes from the scorpion stinger found at the tip.

Naga viper

At 1,349,000 Scoville heat units, the Naga viper is a rare chilli pepper that’s cultivated in the UK. It’s creation was the result of a hybrid of many different chilli peppers and years of cross pollination.

Bhut jolokia

India’s very own bhut jolokia is on the list of the hottest chillies in the world. It is a popular chilli and has received a lot of media attention. It is the first pepper to have scientifically tested over 1 million Scoville heat units.