How Brown Fat Cells Develop (IMAGE) University of Pennsylvania School of Medicine Caption This shows isolated interscapular brown fat tissue fixed and stained by hematoxylin and eosin. Hematoxylin stains DNA in the nucleus purple. The pinkish eosin stain is mitochondria (along with other cytoplasmic proteins), stained stronger in brown fat Credit Sona Rajakumari and Jeff Ishibashi, Perelman School of Medicine, University of Pennsylvania Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.