RNA is a nucleic acid, like DNA, with many fundamental biological roles in when, where, and by how much genes are turned on. Classically, sections of DNA are copied to RNA which are decoded into proteins that carry out cellular functions, but RNAs also have many roles that fall outside of this framework. RNA-Seq is typically used to analyze the amount of each gene's RNA is present in experimental samples ("i.e.", gene expression), as well as changes made during RNA processing ("e.g.", alternative splicing, editing, mutations, or fusions between multiple RNAs). RNA-Seq requires molecular biology and computational steps. Recent advances in RNA-Seq include the ability to study single cells and entire single RNA molecules. It has broad applications across the life sciences from agriculture to medicine.