Blotting Technique: In this technique, DNA segments are derived on agarose gel by electrophoresis and are then transferred and stabilised on a nitrocellulose filter. These are then identified by hybridization with DNA probes. This process is called the blotting technique. 1. Southern Blotting Technique: E.M. Southern (1975) first used this method and transferred DNA segments on the nitrocellulose filter. This technique was named a Southern blotting technique. By this technical analysis of DNA, segments are done. 2. Northern Blotting Technique: Alwin et al (1979) transferred RNA segments after electrophoresis on amino benzyl oximetry (OBM) membrane in place of nitrocellulose filter. This technique was named as Northern blotting technique. This technique is used for the analysis of RNA segments. 3. Western Blotting Technique: Tobin et al. (1979) first break down proteins into polypeptides with the help of sodium-do-decyl sulphate (SDS). After separating them with the help of electrophoresis, transferred these on a nitrocellulose filter or nylon membrane. These were then decoded on an X-ray plate and identified the protein. By this technical analysis of proteins is done. This is called the western blotting technique.