1. A three-dimensional, engineered, biological tumor model comprising: a. stromal tissue; and b. tumor tissue; the tumor tissue comprising cancer cells, the tumor tissue in contact with the stromal tissue to form the three-dimensional, engineered, biological tumor model; provided that the stromal tissue was bioprinted from a stromal bio-ink comprising human preadipocytes exposed to a differentiation signal and the tumor tissue was bioprinted from a tumor bio-ink.