Nucleolus plays a vital role in enhancing rRNA production and maintaining ribosome biogenesis in tumor cells, making the nucleolus a desirable target for genetic and oncological research. The most convenient method for nucleolus monitoring is fluorescent microscopy, combining high efficiency and accessibility. Nevertheless, currently available fluorescent visualization methods are unsuitable for live-cell monitoring of nucleolus because they require continuous labeling. To address this issue, we have developed a genetically encoded Light-Activated Nucleolus Sensing (LANS) system for real-time nucleolar visualization. The combination of eMags domains and reader domain of DPF3 protein, responsible respectively for the light-induced dimerization and targeting the nucleolus, allowed LANS system to efficiently target nucleolus in several cancer cell lines without affecting cell morphology. This system makes it possible to increase the representation of the LANS2 sample in the nucleolus by 1.5 times relative to the fluorescence intensity values obtained before irradiation of the nucleolus. LANS holds the potential to accelerate the search for new drugs and enhance the primary screening of drug compounds in in vivo models.