Magnetic or non-magnetic microspheres, populations of magnetic or non-magnetic microspheres, and methods for forming magnetic or non-magnetic microspheres are provided. One microsphere configured to exhibit fluorescent and magnetic properties includes a core particle and a monolayer of magnetic particles coupled to a substantial portion of a surface of a core particle. About 60% to about 90% of a surface of a core particle is covered by the monolayer of magnetic particles. The microsphere also includes an outer polymer layer surrounding or encapsulating both the monolayer of magnetic particles and the core particle. One population of magnetic or non-magnetic microspheres is configured to exhibit fluorescent and magnetic properties includes two or more subsets of magnetic fluorescent microspheres. The two or more subsets of microspheres are configured to exhibit different fluorescent and/or magnetic properties. Individual microspheres in the two or more subsets are configured as described herein.