In an interview conducted during the 2021 Genitourinary Cancers Symposium, Peter Reisz, MD, a urologic oncology fellow at Memorial Sloan-Kettering Cancer Center, New York, NY, discusses the use of single-cell RNA sequencing to assess the heterogeneity of tumors and the immune microenvironment. High luminal gene expression was identified across all samples. Additionally, the tumor microenvironment was heterogeneous, with enhanced infiltration of macrophages in high-grade disease.