steps to validate new models, including three-dimensional human tissue models, that improve regulatory decisionmaking in preclinical, clinical, labeling, and postmarket safety and efficacy testing, or other uses by product sponsors. 3. Guidance with respect to three-dimensional human tissue models (a) In general Not later than December 31, 2018, the Secretary of Health and Human Services, acting through the Commissioner of Food and Drugs, shall issue guidance addressing— (1) the development and use of novel tools for toxicology and efficacy testing, including three-dimensional human tissue models