Photochromic dye (pyrene)-conducting polymer (polypyrrole) core-shell nanomaterials were fabricated using microemulsion micelles as nanoreactors. The adsorption state of pyrene was tunable over a wide range with a small pyrene loading because of the phase separation and the packing constraints of the pyrene crystal. This methodology provides a facile way to control the emission of organic dyes, and also presents a new concept of nano-hybrids for electronic devices.