The study by Genovese et al. investigates the prevalence and implications of clonal hematopoiesis, the expansion of a single hematopoietic stem cell lineage, in the context of blood cancer risk. The researchers analyzed whole-exome sequencing data from 12,380 Swedish individuals, unselected for cancer or hematologic phenotypes, to identify somatic mutations. They found that clonal hematopoiesis with somatic mutations was more common in older individuals (10% of those over 65 years old) compared to younger individuals (1% of those under 50 years old). The most frequently mutated genes were *DNMT3A*, *ASXL1*, and *TET2*, which are also implicated in hematologic cancers. Clonal hematopoiesis was a strong risk factor for subsequent hematologic cancer (hazard ratio, 12.9; 95% CI, 5.8 to 28.7) and was associated with reduced overall survival (hazard ratio for death, 1.4; 95% CI, 1.0 to 1.8). The study also demonstrated that clonal hematopoiesis can be detected early, potentially enabling early detection and intervention for hematologic cancers.The study by Genovese et al. investigates the prevalence and implications of clonal hematopoiesis, the expansion of a single hematopoietic stem cell lineage, in the context of blood cancer risk. The researchers analyzed whole-exome sequencing data from 12,380 Swedish individuals, unselected for cancer or hematologic phenotypes, to identify somatic mutations. They found that clonal hematopoiesis with somatic mutations was more common in older individuals (10% of those over 65 years old) compared to younger individuals (1% of those under 50 years old). The most frequently mutated genes were *DNMT3A*, *ASXL1*, and *TET2*, which are also implicated in hematologic cancers. Clonal hematopoiesis was a strong risk factor for subsequent hematologic cancer (hazard ratio, 12.9; 95% CI, 5.8 to 28.7) and was associated with reduced overall survival (hazard ratio for death, 1.4; 95% CI, 1.0 to 1.8). The study also demonstrated that clonal hematopoiesis can be detected early, potentially enabling early detection and intervention for hematologic cancers.