Brown adipose tissue (BAT) has become a major focus of metabolism research in recent years owing to its anti-obesity properties. In this issue of Best practice and Research Clinical Endocrinology and Metabolism, we have brought together expert contributions from researchers on the subject of BAT. The first chapter by Kirsi Virtanen describes preliminary findings of BAT in humans since the early 1900s and its detection in adults in 2009 using functional imaging with positron emission tomography. The second chapter by Florian Kiefer on browning and thermogenic programming addresses the differences between white, beige and brown fat. It also reviews internal factors behind browning.

Implications of thermogenic activity of BAT for metabolic and cardiovascular health and ageing are reviewed in the third and fourth chapters. In addition, Christian Schlein and Joerg Heeren describe connections between BAT activation and long-chain fatty acids and mechanism through which BAT is involved in eliminating harmful lipids from circulation. Denis Blondin and André Carpentier provide a critical view of the limitations of current methods in detecting BAT mass and its activity.

The efforts to find activators of BAT have been numerous over the past few years. The last chapters summarize current knowledge about internal and external factors enhancing browning, BAT activity, or both. Thyroid hormones, incretins and vitamins are reviewed by Francesc Villarroya and co-workers. Miguel López, Manuel Tena-Sempere summarize the current data on oestrogens as regulators of energy metabolism both at central and peripheral level. Masayuki Saito and coworkers have studied cold-induced BAT activation extensively. They have been pioneers in demonstrating that several dietary molecules, such as capsaicins and capsaicin analogs, also seem to promote BAT activity and browning.

I hope that readers will find that the present special volume provides both a summary of the current state of the knowledge as well as a guide to exciting new areas of discovery. Practice points and Research agenda are included in the chapters to facilitate that.