Analysis of single cells has become a key technique in biological and biomedical research. Single-cell genomics, transcriptomics, epigenomics, and proteomics now allow many enduring questions in biological and biomedical sciences to be answered. The new single-cell approaches offer the potential to revolutionize our understanding of diseases and associated biological processes, with the capacity to reveal the intercellular heterogeneity within a specific tissue at an unprecedented resolution. The single cell technology has proven to be a valuable tool to explore DNA, RNA, or proteins in one single cell at a time. Using single-cell level features, we can infer cell lineages, identify subpopulations and highlight cell-specific biological characteristics. Moreover, single-cell analyses have already demonstrated their utilities in the clinical applications, ranging from characterizing cancer cells subpopulations, highlighting specific resistance mechanisms to being used as diagnostic tools. For example, by employing single-cell sequencing to circulating tumor cells, metastasis and progression diagnoses may aid in therapeutic design. Single-cell sequencing analyses have been applied in the field of virology, providing new ways to explore viral diversity and cell response to viral infection. Single-cell RNA sequencing have been used to dissect plant tissue organization, developmental dynamics, and physiological responses. Single-cell analysis have made increasingly significant contributions to our understanding of the role that somatic genome variations play in neuronal diversity and behaviors In this book, the technologies recently developed for single cell isolation, genome acquisition, transcriptome, and proteome analyses, their applications and the future potentials are thoroughly discussed.