B-cell
Type of white blood cell and more specifically a type of lymphocyte which produces antibodies (immunoglobulins). B-cells (like other hematopoietic cells) originate in the marrow and start maturation in the Bone marrow and complete their maturation process in germinal center of secondary follicles within secondary lymphoid tissues/organs such as lymph nodes, mucosa associated lymphoid tissue (MALT), or spleen. Remember B-cell for Bone marrow and T-cell for Thymus (B-cells start maturation in Bone marrow while T-cells mature in the Thymus.
Atlas Link: Mature B-cells