Single- or multicolor-encoded microspheres are created by confining water-soluble CdTe nanocrystals with different sizes within hydrogel microspheres of N-isopropyl-acrylamide and 4-vinylpyridine copolymer based on the pH-responsive swelling behavior of the get (see Figure). The emission intensity level and color of the resulting fluorescent spheres can be manipulated simply by changing the concentrations of the different-sized NCs and their molar ratios.