The Ising model is one of the standard models in statistical physics. Since 1969 more than 16,000 publications have appeared using this model. The model was introduced by Ernst Ising in his doctoral dissertation. His life covers most of the past century and was interwoven with striking events in science and politics. It was characterized as a "walk on a tightrope". In this paper some biographical notes and milestones of the early development of the Ising model are given.