Aptamers are short sequences of artificial DNA or RNA that bind to specific target molecules such as peptides, proteins, carbohydrates, toxins, small molecules or live cells. In molecular biology, systematic evolution of ligands by exponential enrichment (SELEX) is a combinational chemistry technique used for generating oligonucleotides of either single-stranded DNA or RNA that specifically bind to a target ligand or ligands. Aptamers can be classified into two types, namely, peptide aptamers and DNA/RNA aptamers. There are several applications of aptamers, which can be categorized into therapeutic, diagnostic, reagent production, and engineering. Aptamers are suitable in diagnostic applications since they exhibit properties of tailored specificity and affinity, high thermal stability, and scalability of production. In therapeutics, aptamers can replace antibodies and facilitate the controlled release of therapeutic biomolecules such as growth factors. This book outlines the biotechnological applications of aptamers in detail. It aims to equip students and experts with the advanced topics and upcoming concepts in this area of study.