The ability to control cell function is one of the challenges for cell-based therapy in regenerative medicine. In this study, we describe a novel method to fabricate cell hydroxyapatite (HAp) nanocrystal composites to modulate cellular microenvironment. By preparation of layer-by-layer nanometer-sized extracellular matrix films onto cell surfaces, HAp nanocrystals were fabricated onto cell surfaces without cytotoxicity. This technology can modulate cellular functions such as adhesion, growth, and differentiation.