In the 1950s Kurt Lewin created a new discipline of management: change management. Managers and leaders had always been tasked with instigating and facilitating transitions, but Lewin’s work represented the first well-researched theoretical model describing the change process. Lewin believed organizational change happened in three stages: unfreezing, change and freezing.

The unfreezing stage involved overcoming inertia and dismantling the existing “mind set.” The defense mechanisms of individuals in the organization have to be bypassed and people need to be made change-ready. The change stage is a period of confusion and transition, where the old ways are being challenged and individuals do not have a clear picture as to what the new ways will look like. In the freezing stage (often mislabeled the refreezing stage), the changes are solidified and a new mindset crystallizes, bringing everyone’s comfort level back to where it was.

The three-stage model developed by Lewin has continued to be discussed and built upon. Most notably, John Kotter, a professor at Harvard Business School, developed his own model for leading change that involved eight steps or actions to be taken. These steps correlate nicely with Lewin’s three-stages and strengthen the foundation Lewin created.