Chinese Hamster ovary cells (CHO cells) are an epithelial cell line derived from the ovary of the Chinese hamster. They are widely used in biological and medical research. The image represents the Chinese Hamster ovary cells (CHO cells), which are engineered to overexpress Delta Opioid Receptor (DOR), a type of G protein-coupled receptor that is involved in pain sensation. These receptor-expressing cells serve as a valuable in-vitro model for various experiments, such as studying opioid receptor function and screening of new therapeutic compounds to see if they can bind to and affect opioid receptors, which is useful for the development of new drugs.