In 2015, our efforts were focused on clarify if MPCs arise from an unique in vivo progenitor and eventually identify it in human adult BM aspirates. Starting from the MPC phenotype, we firstly fractionated BM-MNCs into three different subpopulations: CD105+MSCA-1+, CD105+MSCA-1neg and CD31+MSCA-1neg and cultured them for 6-7 days in pooled human AB-type serum (PhABS)-containing medium, resembling the MPC-selective conditions except for the application of hydrophilic TC-treated plastics in order to create a MPC-promoting and MSC-permissive culture conditions. As predicted by their immunophenotype in vitro, MPC were detected only in the cultured CD31+MSCA-1neg fraction but interestingly without any signs of fibroblastoid MSC-like cells despite the permissive attaching properties of the  substrate. As expected MSC-like cells were instead detected, proliferating, in the cultured CD105+MSCA-1+ fraction. However, in human adult BM a plethora of mononuclear cells express CD31 including various precursors and mature elements of the myeloid lineage. Even if immunomagnetic cell sorting confirmed the existence of MPC-progenitor(s) in the CD31+CD14/CD66neg , a more deep investigation of CD31-positive sub-fractions were needed. With this purpose, we analyzed hBM-MNCs combining CD31 with an other myeloid marker, also positive on MPCs,  as CD18 by flow cytometry. Interestingly, as both CD31 and CD18 have been expressed by hBM-MNCs in three different level of fluorescence intensity (dimintermediate and bright), plotting events in a CD31 vs CD18 cytogram allowed visualizing a "map" of distribution of the various positive subpopulations. Then, reverse gating strategy applying lineage markers identified seven regions of the plot associated to specific bone marrow populations including: lymphocytes (CD3/CD20), granulocytes (CD66), monocytes (CD14), plasma cells (CD138) and hemopoietic and endothelial stem/progenitor cells (CD34). Nonetheless, a further recognizable population CD31brightCD18dim resulted negative for any of the lineage markers applied (Figure XXXX). We then demonstrated that this eight population (Pop#8) resulted the unique bone marrow fraction able to generate MPCs in culture with PhABS-containing medium. Characterization of Pop#8 revealed an homogeneous population expressing high levels of CD31 and CD64, weak expression of CD33, CD13, CD45 and negative for the lineage marker CD14