This issue of the journal is dedicated to outline emerging optical technologies that have the potential to improve early cancer detection, screening, diagnosis, and treatment. The authors have briefly reviewed the progress of emerging technologies, described some of the emerging optical systems or methods in their laboratories, and then discuss the barriers for their translation to clinical applications. The scope of the manuscripts includes both endogenous and exogenous contrast agents, including molecular probes. The first four papers address early cancer detection, the remaining four papers address cancer diagnosis or image guided therapy, including either molecular or multi-modality imaging methods.