The article "Hydrogels for Active Photonics" explores the emerging field of hydrogel-based photonics, which offers deformable geometric parameters in response to external stimuli, providing a promising solution for active photonics. The authors review recent advancements in hydrogel-based photonics and micro/nanofabrication techniques, including film growth, photolithography (PL), electron-beam lithography (EBL), and nanoimprint lithography (NIL). They highlight the unique properties of hydrogels, such as their deformable behavior and optical transparency, and discuss how these properties can be exploited for dynamic optical responses in photonic devices. The article also provides insights into future directions and potential practical applications of deformable hydrogel photonics. Key applications include humidity sensors, colorimetric sensors, and plasmonic color displays, demonstrating the versatility and potential of hydrogel-based photonics. The authors conclude by emphasizing the need for standardized performance characterization and testing protocols to ensure the reliability and durability of hydrogel-based photonic devices under various environmental conditions.The article "Hydrogels for Active Photonics" explores the emerging field of hydrogel-based photonics, which offers deformable geometric parameters in response to external stimuli, providing a promising solution for active photonics. The authors review recent advancements in hydrogel-based photonics and micro/nanofabrication techniques, including film growth, photolithography (PL), electron-beam lithography (EBL), and nanoimprint lithography (NIL). They highlight the unique properties of hydrogels, such as their deformable behavior and optical transparency, and discuss how these properties can be exploited for dynamic optical responses in photonic devices. The article also provides insights into future directions and potential practical applications of deformable hydrogel photonics. Key applications include humidity sensors, colorimetric sensors, and plasmonic color displays, demonstrating the versatility and potential of hydrogel-based photonics. The authors conclude by emphasizing the need for standardized performance characterization and testing protocols to ensure the reliability and durability of hydrogel-based photonic devices under various environmental conditions.