In bone tissue engineering, it is desirable to use materials to control the differentiation of mesenchymal stem cell populations in order to gain direct bone apposition to implant materials. It has been known for a number of years that microtopography can alter cell adhesion, proliferation and gene expression. More recently, the literature reveals that nanotopography is also of importance. Here, the reaction of primary human osteoprogenitor cell populations to nanotopographies down to 10 nm in size is considered. The topographies were originally produced by colloidal lithography and polymer demixing on silicon and then embossed (through an intermediate nickel shim) into polymethylmethacrylate. The biological testing considered cell morphology (image analysis of cell spreading and scanning electron microscopy), cell cytoskleton and adhesion formation (fluorescent staining of actin, tubulin, vimentin and vinculin) and then subsequent cell growth and differentiation (fluorescent staining of osteocalcin and osteopontin). The results demonstrated that the nanotopographies stimulated the osteoprogenitor cell differentiation towards an osteoblastic phenotype.