This document provides a history of the development of the Gray Matrix, a model for understanding spiritual growth and receptivity to Christian messages. It traces the model back to influences on the author during his time in Laos in the 1960s-70s and his studies under James Engel at Wheaton College in the 1970s. The author refined Engel's scale by adding an attitudinal dimension, creating the first two-dimensional model. He published and promoted the Gray Matrix model in the 1980s through his work with FEBC and conferences like Wheaton '83, helping establish it as a framework for strategic media-based ministry.