To understand the glass electrode needs knowledge from more than one level. The construction ofthe glass electrode is one part, an other is the composition and structure of glass. The Nernstequation have an important role, but also the sources of errors in the analysis and the calibration ofthe glass electrode. Focus for this article is how the glass electrode really works and how Gibbs freeenergy made the potential dependent of the concentration of H+and gives the logarithm to thefunction. Nikolskii's ion exchange theory starts to explain the question about how the potentialcreates and Baucke's dissociation mechanism made it more explicit.