P is the assignee of the '929 patent which claims methods for preparing multi-cryopreserved hepatocytes (a type of liver cell). Human hepatocytes are a useful laboratory model for evaluating drug candidates. They have a short lifespan which causes an inconsistent and limited supply. The only sources of fresh hepatocytes are liver resections or non-transplantable livers of multi-organ donors. Hepatocytes become available at unpredictable times. Researchers need a pool of hepatocytes from a larger group of different liver donors to minimize the effect of outliers. The '929 patent uses a method for multi-cryopreserving hepatocyte cells and from the results, P sells multi-cryopreserved hepatocyte products. D also sells pooled multi-cryopreserved hepatocyte products, which P alleges involve performing a process infringing the '929 patent. P sued D for infringement and moved for a preliminary injunction. The district court found that P had shown a likelihood of success on the merits. It also considered D's defenses: non-infringement, obviousness, written description, and inequitable conduct. The court granted P a preliminary injunction. D appealed