It produces 300 times more heat than any other organ in the body and it prevents a baby from freezing to death if left in the cold.
Scientists in England have discovered that brown fat is a good thing because it produces lots of heat by burning calories.
Unlike white fat, which clings to our hips, brown fat keeps the weight off. And that's why the race is on to find out more about brown adipose tissue, also known as brown fat, and how humans could use it to our advantage, the BBC reports on its site.
When we're born we have lots of brown fat in our bodies, wrapped round the central organs to keep us warm, to help us adapt to life outside the womb.
As we grow, however, the brown fat content of our bodies decreases.
The BBC says researchers at the University of Nottingham have been using heat-seeking technology to find out if brown fat is still present in children and adults.
Prof. Michael Symonds and Dr. Helen Budge from the University's School of Clinical Sciences say their research, published in the Journal of Pediatrics, shows that the neck region in healthy children produces heat.
"There is only about 50g of brown fat in the neck region and it switches on and off throughout the day as it's exposed to different temperatures or if you exercise or eat," says Prof. Symonds.
He says that the challenge is now to use this knowledge to find out what factors might switch on brown fat, and therefore prevent excess weight gain.
"The more we know about what switches on brown fat the better. It may have an immediate effect which can be retained as you get older. This may provide new insights into the role of brown fat in how we balance energy from the food we eat, with the energy our bodies use up."