The bulk tissue is a heterogeneous mixture of various cell types, which is depicted as a skein of intertwined threads with diverse colors each of which represents a unique cell type. Single-cell omics analysis untangles efficiently the skein according to the color by providing information of molecules at individual cells and interpretation of such information based on different cell types. The molecules that can be profiled at the individual cell by single-cell omics analysis includes DNA (bottom middle), RNA (bottom right), and protein (bottom left). This special issue reviews single-cell technologies and computational methods that have been developed for the single-cell omics analysis and how they have been applied to improve our understanding of the underlying mechanisms of biological and pathological phenomena at the single-cell level.