Cell culture is a term that refers to the growth and maintenance of cells in a controlled environment outside of an organism. A successful stem cell culture is one that keeps the cells healthy, dividing, and unspecialized.Stem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types.Stem cells can now be grown and transformed into specialized cells with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture. The culturing of stem cells is the first step in establishing a stem cell line—a propagating collection of genetically identical cells. Cell lines are important because they provide a long-term supply of multiplying cells that can be shared for research and therapy development.The present study aimed to clarify the ability of human bone marrow mesenchymal stem cells (BM- MSCs) to differentiate into osteoblasts, chondrocytes and neuronal cells.The work was divided into 4 main parts:І. Isolation, propagation, and identification of human BM- derived MSCs: Human BM-MSCs was isolated and cultured then identifid by Morphology (their adhesiveness and fusiform shape) and FACs analysisII. Differentiation of human BM- derived MSCs into osteoblasts: by adding osteogenic supplements as dexamethasone, β-glycerophosphate, BMP2 and L-ascorbic acid 2-phosphate; then identifid by morphology, detection of Osteonectin gene expression by RT-PCR, biochemical analysis of Calcium and Alkaline phosphatase and staining of differentiated osteoblasts by Alizarin red stain. III. Differentiation of human BM- derived MSCs into chondrocytes: by adding chondrogenic supplements as recombinant human TGFβ3, insulin, ascorbate 2-phosphate and dexamethasone; then identifid by morphology, detection of collagen type II gene expression by RT-PCR and staining of differentiated chondrocytes by Alcian blue stain.IV. Differentiation of human BM- derived MSCs into neuronal cells: by adding BDNF and NGF, then identifid by morphology and detection of tyrosine hydroxylase and nestin gene expression by RT-PCR.In the present study we could differentiate human bone marrow derived mesenchymal stem cells (BM- MSCs) in vitro into osteoblasts, chondrocytes and neuronal cells.