A single-cell landscape of the multicellular ecosystem in HCC, comprising cancer stem cells, liver stem cells, progenitor cells, mucosal cells, CD4+ T cells, CD8+ cytotoxic T cells, Treg cells, plasma cells, naive B cells, regulatory B cells, natural killer cells, macrophages, and M1 macrophages, was first described, thus revealing the diversity of the cellular ecosystem in HCC. The gene discussed is CD4; the disease is cancer.