The advent of single-cell RNA sequencing (scRNA-seq) has transformed our understanding of the biological world by providing unprecedented insights into the intricate realm of cellular individuality. The scRNA-seq technique has been extremely useful in unraveling rare and complex cell populations and dynamic cellular states, thereby elegantly capturing the nuances of heterogeneity that otherwise remain masked by bulk RNA sequencing. This capacity to delineate cellular diversity at the resolution of a single cell has not only revolutionized fundamental biology but also unveiled transformative avenues in precision medicine. The art of dimensionality reduction, clustering and lineage inference together transform vast datasets into structured biological narratives. The narrative further explores emerging frontiers, including multimodal single-cell profiling, spatial transcriptomics and integrative frameworks that elegantly combine transcriptomes, proteomes, and epigenomes. Beyond its technological sophistication, scRNA-seq has emerged as a potent lens for investigating complex biological processes of immunity, metabolism, developmental biology, neurobiology, or cancer biology. This chapter provides an overview of the scRNA-seq highlighting major applications of this technique in various biological domains. It describes the workings of scRNA-seq from the meticulous isolation of individual cells and the development of sophisticated library preparation techniques to the advanced sequencing methods and computational pipelines that transform the raw data into valuable insights. Overall aim of the chapter is to showcase the potential of the scRNA-seq technique, which continues to advance the boundaries of biological discoveries by providing not only the huge datasets but also an atlas of cellular world at the unparalleled resolution.