Aptamers are all new ligands with a high affinity for considerably differing molecules ranging from large targets as proteins over peptides,complex molecules to drugs and organic small molecules or even metal ions.These molecules are identified and selected through an in vitro process called systematic evolution of ligands by exponential enrichment(SELEX).Aptamers are widely used,including medical and pharmaceutical basic research,drug development,diagnosis,and therapy.Analytical and separation tools bearing aptamers as molecular recognition and binding elements are another big field of application.The SELEX method was modified over the years in different ways to become more efficient and less time consuming,to reach higher affinities of aptamers selected and higher automation of process.In reviewing this technology,the article covers the topic,following a general introduction,under the headings: the SELEX protocol,the development of aptamers by use of SELEX,and the application of aptamers in food safety.