Crop yield is driven by the spatial and temporal interactions of soil, plant, atmosphere, pest, and diseases. Therefore, agronomic practices must be tailored to such variability. This management concept is embedded into the formal definition of Precision Agriculture. While technology has progressed significantly over the last twenty years, the key concepts of managing such spatio-temporal variability are still at the core of it. Overall, the spatio-temporal management of agricultural fields follows two main philosophies, sensor-based and map-based management. The former utilizes on-the-go sensors for the real time scanning of crop status to adjust the agronomic input. The latter utilizes data from sensors and/or yield monitor to define areas within the field that have similar yield limiting factors. The concept of management zone (MZ) was introduced in the late 1980s. This book chapter explores the main developments and steps of defining and using MZ for improving agronomic management.