The GreenSeeker handheld crop sensor, an easy-to-use measurement device designed to assess the health of a crop, was introduced by Trimble on 6 August 2012. By positioning the sensor over a plant and pulling the trigger, the GreenSeeker instantly calculates the Normalized Difference Vegetation Index (NDVI), which represents the health of the plant. Users can better determine the overall health and needs of a crop by gathering several readings from plants throughout a field. This can result in a more efficient use of fertilizer, which benefits both the farmer’s bottom line and the environment. Before farmers and farm advisers can apply this technology, it needs to be calibrated locally. Through the MasAgro project, the calibration of the GreenSeeker is conducted by national collaborators in 18 states in Mexico for its use in wheat and maize. CIMMYT is also involved in the calibration of the sensor in Asia and Africa.