Hydrogels have emerged as promising materials for active photonics due to their ability to respond to external stimuli, enabling dynamic optical properties. This review discusses recent advancements in hydrogel-based photonics and micro/nanofabrication techniques. Hydrogels, which are three-dimensional polymer networks, can swell or deswell in response to stimuli such as temperature, pH, or humidity, altering their refractive index and optical properties. This tunability makes them suitable for applications in optical devices, sensors, and displays. Various fabrication techniques, including film growth, photolithography (PL), electron-beam lithography (EBL), and nanoimprint lithography (NIL), have been employed to create hydrogel-based photonic devices. These techniques allow for the precise control of hydrogel structures, enabling the development of devices with tunable optical responses. For example, hydrogel-based devices have been used to create humidity-sensitive colorimetric sensors, tunable optical filters, and dynamic displays. The integration of hydrogels with photonic structures has enabled the creation of devices that can respond to environmental changes, such as humidity, temperature, or pH, leading to applications in sensing, imaging, and optical communication. Hydrogels have also been combined with other materials, such as metal nanoparticles and polymers, to enhance their optical and mechanical properties. For instance, hydrogels embedded with metal nanoparticles have been used to create plasmonic structures that can modulate light in response to environmental stimuli. Additionally, hydrogels have been used in the fabrication of metasurfaces, which are nanostructured materials that can control light at the nanoscale. These metasurfaces have potential applications in optical encryption, sensing, and imaging. The review highlights the potential of hydrogels in photonic applications, emphasizing their tunable optical properties, compatibility with various fabrication techniques, and ability to respond to external stimuli. However, challenges remain in terms of standardizing measurement methods and optimizing the performance of hydrogel-based devices. Future research should focus on improving the response time, deformation range, and optical characteristics of hydrogel-based photonic devices to enhance their practical applications in fields such as sensing, imaging, and optical communication.Hydrogels have emerged as promising materials for active photonics due to their ability to respond to external stimuli, enabling dynamic optical properties. This review discusses recent advancements in hydrogel-based photonics and micro/nanofabrication techniques. Hydrogels, which are three-dimensional polymer networks, can swell or deswell in response to stimuli such as temperature, pH, or humidity, altering their refractive index and optical properties. This tunability makes them suitable for applications in optical devices, sensors, and displays. Various fabrication techniques, including film growth, photolithography (PL), electron-beam lithography (EBL), and nanoimprint lithography (NIL), have been employed to create hydrogel-based photonic devices. These techniques allow for the precise control of hydrogel structures, enabling the development of devices with tunable optical responses. For example, hydrogel-based devices have been used to create humidity-sensitive colorimetric sensors, tunable optical filters, and dynamic displays. The integration of hydrogels with photonic structures has enabled the creation of devices that can respond to environmental changes, such as humidity, temperature, or pH, leading to applications in sensing, imaging, and optical communication. Hydrogels have also been combined with other materials, such as metal nanoparticles and polymers, to enhance their optical and mechanical properties. For instance, hydrogels embedded with metal nanoparticles have been used to create plasmonic structures that can modulate light in response to environmental stimuli. Additionally, hydrogels have been used in the fabrication of metasurfaces, which are nanostructured materials that can control light at the nanoscale. These metasurfaces have potential applications in optical encryption, sensing, and imaging. The review highlights the potential of hydrogels in photonic applications, emphasizing their tunable optical properties, compatibility with various fabrication techniques, and ability to respond to external stimuli. However, challenges remain in terms of standardizing measurement methods and optimizing the performance of hydrogel-based devices. Future research should focus on improving the response time, deformation range, and optical characteristics of hydrogel-based photonic devices to enhance their practical applications in fields such as sensing, imaging, and optical communication.