We have investigated the capacity of activated carbon cloth to support the growth and differentiation of human mesenchymal umbilical-cord stromal stem cells. Our results demonstrate that this scaffold provides suitable conditions for the development of cell-derived matrix proteins and facilitates the growth of undifferentiated stem cells with the ability to induce osteogenic and chondrogenic differentiation. Immunoflourescence staining revealed extensive expression of collagen in all the samples, and collagen type II and osteopontin within the samples cultivated in specific differentiation-inducing media. Cell growth and the formation of natural collagen, calcium–magnesium carbonate and hydroxyapatite crystals, together with the self-assemblage of collagen to produce suprafibrillar arrangements of fibrils all occur simultaneously and can be studied together ex vivo under physiological conditions. Furthermore, the spontaneous differentiation of stem cells cultured on activated carbon cloth with no osteogenic supplements opens up new possibilities for bone-tumour engineering and treatment of traumatic and degenerative bone diseases.