The　photon-to-photon　conversion　process　has　attracted　great　attention　as　it　can　carry　out　the　conversion　of　photons　in　different　wavelength　regions　and　use　the　characteristics　of　different　bands　to　achieve　a　variety　of　applications,　including　solar　cells,　temperature　measurement,　information　security,　luminous　display,　and　biomedicine.　According　to　the　process　of　converting　photons　of　different　energy,　the　photon-to-photon　conversion　process　can　be　simply　divided　into　two　categories:　the　downconversion　process　converting　high-energy　photons　to　lower-energy　photons　and　the　upconversion　process　converting　the　low-energy　photons　to　higher-energy　photons.　Nanoscale　materials　and　devices　used　in　photon-to-photon　conversion　have　been　widely　concerned　and　have　been　successfully　applied　in　many　fields,　while　the　corresponding　summaries　of　the　representative　work　are　very　few　as　far　as　we　know.　In　this　review,　recent　advances　and　progress　in　photon-to-photon　conversion　in　nanoscale　materials　and　devices　and　their　applications　are　summarized.　Around　this　field,　we　then　analyzed　and　summarized　the　prospects　and　challenges　for　its　development　in　the　future.