Disentangling the neuroendocrine systems, which regulate energy homeostasis and adiposity, has been a long-standing challenge in pathophysiology, with obesity as an increasingly important public health problem. Adipose tissue has been considered for a long time as only a passive organ for the storage of excess energy in the form of fat. However, compelling evidence gathered during the last decades has revealed adipocytes as extremely active endocrine secretory cells playing a relevant role in the regulation of metabolism, reproduction, immunity, blood pressure, fibrinolysis, coagulation, and angiogenesis, among others. An extensive cross talk at a local and systemic level in response to specific external stimuli or metabolic changes underpins the multifunctional characteristics of fat cells, which rely on their ability to secrete a large number of hormones, growth factors, enzymes, cytokines, complement factors, and matrix proteins, collectively termed as adipokines or adipocytokines, at the same time expressing receptors for most of these factors.