BACKGROUND:Visualization of chromosomal loci location and dynamics is crucial for understanding many fundamental intra-nuclear processes such as DNA transcription,replication,and repair.OBJECTIVE:Here,we will describe the development of fluorescence labeling methods for chromatin imaging,including traditional as well as emerging chromatin labeling techniques in both fixed and live cells.We will also discuss current issues and provide a perspective on future developments and applications of the chromatin labeling technology.METHODS:A systematic literature search was performed using the PubMed.Studies published over the past 50 years were considered for review.More than 100 articles were cited in this review.RESULTS:Taking into account sensitivity,specificity,and spatiotemporal resolution,fluorescence labeling and imaging has been the most prevalent approach for chromatin visualization.Among all the fluorescent labeling tools,the adoption of genome editing tools,such as TALE and CRISPR,have great potential for the labeling and imaging of chromatin.CONCLUSION:Although a number of chromatin labeling techniques are available for both fixed and live cells,much more effort is still clearly required to develop fluorescence labeling methods capable of targeting arbitrary sequences non-intrusively to allow long-term,multiplexing,and high-throughput imaging of genomic loci and chromatin structures.The emerging technological advances will outline a next-generation effort toward the comprehensive delineation of chromatin at single-cell level with single-molecule resolution.