Western blotting (immunoblotting) is a powerful and commonly used technique that is capable of detecting or semiquantifying an individual protein from complex mixtures of proteins extracted from cells or tissues. The history surrounding the origin of western blotting, the theory behind the western blotting technique, a comprehensive protocol and the uses of western blotting are presented. Lesser known and significant problems in the western blotting field and troubleshooting of common problems are highlighted and discussed. This work is a comprehensive primer and guide for new western blotting researchers and those interested in a better understanding of the technique or getting better results.