To date, analysis of aged mice has failed to detect CH, unless they are challenged by chemotherapy or inflammatory stimuli, whereby CH appears as a small clone size in contrast to what we describe here.21,53 An important highlight of our study is the use of SCIFER to uncover how blood is still being produced in severely HSPC-depleted, but otherwise healthy, animals; canonical methods fail to capture how hematopoiesis was being sustained. This evidence concerns the gene PSMA7 and cyclic hematopoiesis.