1975 Biologist Ed Southern popularizes a method for cutting DNA into manageable bits, arranging these fragments in size order and securing them to a piece of filter paper. In this method, called Southern blotting, radioactively labeled pieces of DNA are washed over this DNA-coated filter, and fragments with complementary sequences stick to their partners on the paper. Exposing the filter to X-ray film (to locate the radioactive labels) allows researchers to identify which sequences match. Molecular biologists use a similar technique for identifying matching RNA sequences. As a pun, they call the method "Northern" blotting. The name sticks.