Nutrient excess, weight gain, and ensuing obesity result in expansion of adipose tissue mass and adipocyte size. The combination of microhypoxia and nutrient excess leads to the eventual death of the adipocyte as well as a characteristic inflammatory response and infiltration of adipose tissue macrophages (ATMs). These macrophages often surround dead adipocytes to form crown-like structures (CLS) and are highly inflammatory in nature, releasing pro-inflammatory cytokines, which work in a paracrine manner to activate the intracellular pro-inflammatory pathways (e.g., JNK and IKK) in neighboring cells and possibly through endocrine mechanisms in distal tissues. This image shows an immunofluorescence of epididymal white adipose tissue (eWAT) from high fat diet-fed mice. Adipocytes and adipose tissue macrophages were stained with the membrane markers Caveolin-1 (blue) and F4/80 (green) respectively.