The study of adipose tissue in the field of toxicologic pathology is in its infancy. However, the increasing global burden of obesity, the impact of obesogens, and the development of drugs to treat obesity and associated health issues have led to a need for more information in this field, especially in the area of pathology evaluation and interpretation. The major adipose tissues include white adipose tissue, brown adipose tissue, and bone marrow adipose tissue. Since adipose tissues are heterogenous, responses in one adipose tissue depot cannot be extrapolated to all adipose tissue depots. Knowledge of lesions and changes typical for the different adipose tissue types must be developed with consistent sampling, standardized across species and gender, an important first step. Adipose tissue changes that occur in nonclinical toxicology studies are mostly adaptive changes related to changes in energy storage, and thermogenic and/or endocrine roles. Insights into differences and similarities across the various adipose tissue types, their origins and functions, and their impacts locally and systemically may reveal new therapeutic targets as well as identify new aspects needing to be addressed in risk and safety evaluation during drug development.