Optical coherence tomography (OCT) is a valuable tool in the cross-sectional observation/analysis of three-dimensional (3-D) biological tissues, and that histological observation is important clinically. However, the resolution of the technology is approximately 10-20 m. In this study, optical coherence microscopy (OCM), a tomographic system combining OCT technology with a microscopic technique, was constructed for observing cells individually with a resolution at the submicrometer level. Cells and 3-D tissues fabricated by cell sheet technology were observed by OCM. Importantly, the cell nuclei and cytoplasm could be clearly distinguished, and the time-dependent dynamics of cell-sheet tissues could be observed in detail. Additionally, the 3-D migration of cells in the bioengineered tissue was also detected using OCM and metal-labeled cells. Bovine aortic endothelial cells, but not NIH3T3 murine embryonic skin fibroblasts, actively migrated within the 3-D tissues. This study showed that the OCM system would be a valuable tool in the fields of cell biology, tissue engineering, and regenerative medicine. (c) 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 481-488, 2017.