Phase change materials (PCMs) offer unique optical and electronic properties that enable their use in photonic applications. Upon transitioning from an amorphous to a crystalline state, their optical properties change significantly, allowing for rapid switching between these states. This property makes PCMs attractive for photonic applications, including all-photonic memories, color displays, and nanophotonic systems. PCMs can be used to create reconfigurable, non-volatile photonic devices, enabling manipulation and control of light. The review discusses the potential of PCMs in emerging photonic applications, ranging from optoelectronic systems with multi-level storage and display capabilities to their integration in nanophotonic systems and metamaterials. The review also highlights the importance of defining PCM properties and their applications in photonic systems. PCMs have been used in optical data storage and non-volatile electronic memories, demonstrating their excellent scaling potential and fast switching speeds. Recent developments in PCM-based photonic applications include integrated optics, color displays, and active plasmonics. The review discusses the potential of PCMs in these applications, highlighting their ability to provide adjustable optical properties and enable new functionalities. The review also discusses the challenges and requirements for implementing PCMs in photonic systems, including the need for low power consumption, high switching speed, and the ability to switch between different states. The review concludes that PCMs have significant potential for future photonic applications, including all-optical computing and photonic memories.Phase change materials (PCMs) offer unique optical and electronic properties that enable their use in photonic applications. Upon transitioning from an amorphous to a crystalline state, their optical properties change significantly, allowing for rapid switching between these states. This property makes PCMs attractive for photonic applications, including all-photonic memories, color displays, and nanophotonic systems. PCMs can be used to create reconfigurable, non-volatile photonic devices, enabling manipulation and control of light. The review discusses the potential of PCMs in emerging photonic applications, ranging from optoelectronic systems with multi-level storage and display capabilities to their integration in nanophotonic systems and metamaterials. The review also highlights the importance of defining PCM properties and their applications in photonic systems. PCMs have been used in optical data storage and non-volatile electronic memories, demonstrating their excellent scaling potential and fast switching speeds. Recent developments in PCM-based photonic applications include integrated optics, color displays, and active plasmonics. The review discusses the potential of PCMs in these applications, highlighting their ability to provide adjustable optical properties and enable new functionalities. The review also discusses the challenges and requirements for implementing PCMs in photonic systems, including the need for low power consumption, high switching speed, and the ability to switch between different states. The review concludes that PCMs have significant potential for future photonic applications, including all-optical computing and photonic memories.