Chemical stimulation with β3-adrenergic receptor agonists has been shown to induce browning in white adipose tissue (WAT), but determination of the quantity and location of this new beige fat mass is a challenge. The difference in mitochondrial abundance between WAT and beige fat suggests that an imaging agent able to quantify mitochondrial expression may be ideal for identifying beige fat mass. TSPO-18kDa (TSPO) is a five transmembrane domain protein located on the outer membrane of mitochondria, which may be detected using positron emission tomography (PET). Hartimath et al. tested the TSPO tracer [18F]FEPPAand found that it may be useful for detecting unstimulated beige adipocytes.