Abstract: A composition and a method for generating clinically safe NK cells derived from non-fully differentiated stem cells are provided. The non-fully differentiated stem cells are co-cultured with endogenous NK cells isolated from adipocyte-containing tissue to generate a high percentage of clinically safe NK cells, where anti-tumor activity of the clinically safe NK cells in vitro is similar to that of endogenous NK cells. Optimized Production of the clinically safe autologous NK cells from stem cells provides platform for treating cancer patients by applying an effective adoptive immunotherapy ranging from the early to terminal stages.