miRNAs involved in B cell development in the bone marrow and periphery. B cells development starts in the bone marrow and achieves a remarkable diversity of immunoglobulin loci by V(D)J recombination. Immature B cells migrate to the secondary lymphoid organs where they are activated by specific antigens. Once they are activated, they undergo proliferation and further differentiation into plasma cells that secrete antibodies or memory B cells that can be reactivated with a secondary infection. There are at least three different types of mature B cells: B1 cells, conventional follicular B2 cells and marginal-zone B cells. miRNAs that are involved in different stages of B cell development are indicated above the arrows. Secondary diversification of the immunoglobulin loci is achieved by SHM and CSR at the germinal center. Abbreviations, CLP: Common lymphoid progenitor; MZB: marginal zone B cells; CB: Centroblasts; CC: Centrocytes; PC: Plasma Cell; Mem: Memory cell; SHM: Somatic Hypermutation; CSR: Class switch recombination.