"Gels used for electrophoresis of nucleic acids and proteins are permeable. This obvious fact didn't dawn on me until I tried to dissolve some agarose by floating it on a solution of sodium perchlorate and noticed a bead of liquid form on the top. I reasoned that if DNA molecules were carried through with the flow it would be possible to capture them on a nitrocellulose membrane, using the setup shown in the sketch. The big thrill came when, at the first attempt, I saw genes lit up as bands after hybridizing with radiolabeled probes. The Journal of Molecular Biology [initially] rejected the first manuscript1 as a 'methods paper' and the sketch is what I sent to people who had heard of the method and wanted to get on and use it."
-- Ed Southern, Oxford University