The development of multifunctional light emitters has emerged as a groundbreaking approach in the field of theranostics, providing seamless integration of diagnostics and therapeutics within a single platform. These advanced materials, including organic dyes, quantum dots, upconversion nanoparticles, and perovskites, exhibit remarkable photophysical properties such as high luminescence efficiency, photostability, and tunable emission wavelengths. By leveraging their multifunctionality, these light emitters enable precise real-time imaging, targeted drug delivery, and noninvasive therapeutic interventions, including photothermal and photodynamic therapy. Moreover, their capacity to respond to specific stimuli, such as pH, temperature, and enzyme activity, facilitates the dynamic monitoring of disease progression and treatment efficacy. Recent innovations in bioconjugation and surface engineering have enhanced biocompatibility and specificity, paving the way for applications in oncology, neurodegenerative disorders, and infectious diseases. However, challenges such as potential toxicity, scalability, and environmental impacts remain critical barriers to widespread clinical adoption. This chapter examines recent advancements, design principles, and emerging trends in multifunctional light emitters, highlighting their transformative potential in personalized medicine and sustainable theranostic strategies. By addressing the current limitations and fostering interdisciplinary collaboration, these novel light-emitting materials hold promises for redefining precision healthcare.