The book deals with the depth nature of leukemic stem cells (LSC) which is attributed to leukemia cell type. Among the other expressing molecular markers, the BAALC gene expression holds a specific place. The BAALC gene seems to be selectively linked with active fraction of Leukemia Stem Cells (aLSC) which, in turn, will allow clinicians to use it actively for aLSC’s burdens estimating at the clinical setting by means standard Real-time qPCR. Meanwhile, the book contains the data of recently carried out author’s studies on the topic which is capable to convince future readers and researches in term-line of these investigations in oncohematology. The book is accounted not only onto hematologists but biologists too who tied their work with in depth studies in oncohematology. In whole, original concept of BAALC-expressing LSC opens a wide avenue for in depth investigations in the field: a) Leukemia and MDS pathogenesis: and b) efficacy assay of new agents and more interesting novel therapeutic approaches on the level of earlier LSCs.