In recent years, the emerging fluorescent carbon dots have shown enormous potentials for biomedical and optoelectronic applications owing to their outstanding characteristics such as good biocompatibility, low cytotoxicity, photostability and versatility in addition to their unique tunable photoluminescence and other exceptional physicochemical properties. In this review, we will update the latest researches on the synthesis, structure, optical and electronic properties of CDs as well as their advanced applications in biomedicine and optoelectronics. We will mainly discuss the applications of CDs in bioimaging with emphasis on stem cells imaging including normal and cancer stem cells, cell nucleus imaging, two-photon fluorescence imaging, red or near-infrared emission for in vivo imaging, cancer therapy including photodynamic therapy, photothermal therapy and chemotherapy, and optoelectronic applications including light emitting diodes and solar energy conversion. Finally, we will size up current challenges on the research of CDs and project future directions of the field. We hope that this review will provide critical insights to inspire new exciting discoveries on CDs from both fundamental and practical standpoints so that the realization of their potential in the biomedical and optoelectronic areas can be facilitated. (C) 2016 Elsevier Ltd. All rights reserved.