A method of identifying an analyte. The method includes providing a plurality of microparticles. The microparticles have optically detectable codes extending along bodies of the corresponding microparticle. The microparticles have the chemical probes attached thereto. Each of the chemical probes is associated with a corresponding one of the codes. The method also includes selectively binding target analytes to the chemical probes on the microparticles to produce labeled microparticles and distributing the labeled microparticles to random locations of a substrate. The method also includes determining the codes for the labeled microparticles in the random array and code positions of the codes in the random array. The method further includes detecting the label on the labeled microparticles in the random array and label positions of the labels in the random array. The method also includes using the code positions and the label positions to analyze the target analyte.