The cellular and molecular mechanisms of magnetic stimulation-based bone regeneration require further understanding at present. To evaluate the phenomenon in the lab, a three-dimensional (3-D) native collagen model was recently developed via plastic compression to produce a cellular, dense and mechanically strong collagen structure. To produce cell-laden models in the study, Zhiyu Yuan and colleagues incorporated osteoblast cells (MG-63 cell line) and magnetic iron oxide nanoparticles (IONPs) into the collagen gels. Using 3-D printing, a magnetic bioreactor was designed and fabricated to support cell growth under static magnetic fields (SMFs). Using polymerase chain reaction (PCR), the researchers determined the impact of SMFs on the regulation and expression of genes related to osteogenesis including runt-related transcription factor 2 (Runx2), osteonectin (ON) and bone morphogenetic proteins 2 and 4 (BMP-2 and BMP-4).