A process for making a micro-array. The process comprises the step of depositing a population of microbeads on a substrate having at least one fiducial. The population being comprised of at least two sub-populations, preferably multiple sub-populations, each comprising a known active agent capable of specific binding with at least one target analyte. The said subpopulations are deposited sequentially and at discrete periods of each other. The process also comprises the step of making images of the substrate after deposition of each subpopulation. The images are then compared using the fiducial as a reference to thereby determine the location of each microbead and to identify the subpopulation, and its known active agent, based on differences between each image. Also disclosed in a system for using the microarray.