The careful characterization of the cell-specific role of Arg1 and Arg2 in mouse models, human cells/organoids, and human cohorts with single-cell and multiomics approaches will allow a deeper understanding of the role of arginase in specific cells and tissues, thus providing better diagnostic, prognostic, and therapeutic strategies to address cardiovascular, hematological, inflammatory, and genetic diseases related to l-arginine metabolism and cancer. The gene discussed is ARG2; the disease is cancer.