RNA-Seq

RNA-Seq (short for "RNA sequencing") is a technique to get snapshots of the continuously changing RNA landscape in a cell.
RNA is a nucleic acid with 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. 
RNAs also have many roles that fall outside this framework. RNA-Seq is typically used to analyze the amount of each gene's RNA in experimental samples. For example, in gene expression and changes made during RNA processing (alternative splicing, editing, mutations, or fusions between 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 in the life sciences from agriculture to medicine.