HepatoPac Kits are in vitro tools used for predicting likely in vivo outcomes and mechanisms of toxicity with respect to transport and metabolism of drugs and chemicals. HepatoPac plates contain micropatterned co-cultures (MPCCs) of primary hepatocytes and stromal cells. This technology replicates the physiological microenvironment of the liver and allows hepatocytes to exhibit normal metabolic activity for over 4 weeks for both short- and long-term toxicology and efficacy studies during preclinical drug discovery. Hepatocyte health, functionality, and liver enzyme activity can be extensively characterized on the HepatoPac platform. HepatoPac products are available with human, rat, dog, or monkey hepatocytes, or in multispecies formats.