There is an interesting yet little known story about a model in the field of Organization Development. Referred to as the Change Formula, it is one of the most practical, widely recognized tools developed in the last 50 years. The formula describes the conditions, that when met, will move an individual, group, or whole system in a direction of their choosing. What is the formula? We share several iterations of it a bit later in this article. First we take you through a review of how history shapes various models, theories, methods, tools, and approaches. Then, we provide an account of the history that shaped the formula. From there, we define and describe the formula with examples of how it can help you as an OD practitioner.