1. A process for making a micro-array comprising the steps of: depositing a population of microbeads on a substrate having at least one fiducial, said population being comprised of at least two sub-populations each comprising a known active agent capable of specific binding with at least one target analyte, wherein said subpopulations are deposited sequentially and at discrete periods of each other; making images of said substrate after deposition of each subpopulation; and comparing said images using said 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.