Researchers have developed ultraflexible organic photonic skin, which integrates electronic components onto the skin to enable health monitoring and information technologies. The system includes three-color, highly efficient polymer light-emitting diodes (PLEDs) and organic photodetectors (OPDs) that are ultraflexible and conformable, with a total thickness of only 3 micrometers, thinner than the epidermal layer of human skin. These devices can be laminated onto the skin to create optoelectronic skins (oe-skins) that provide multiple electronic functions such as sensing and displays. The ultraflexible reflective pulse oximeter, made by integrating green and red PLEDs with OPDs, can unobtrusively measure blood oxygen levels when applied to a finger. On-skin seven-segment digital displays and color indicators can visualize data directly on the body. The study demonstrates the feasibility of electronic functionalization of human skin using ultrathin devices. The devices are fabricated on 1-micrometer-thick polymeric films and laminated onto curved surfaces. The passivation layer, composed of alternating inorganic (SiON) and organic (Parylene) layers, ensures the devices can operate in ambient conditions. The ultraflexible PLEDs and OPDs exhibit high performance, with excellent electrical characteristics and mechanical flexibility. The PLEDs have high external quantum efficiency and luminance, while the OPDs show good light sensitivity and stability. The devices are highly flexible and can withstand extreme stretching and bending, making them suitable for wearable and medical applications. The ultraflexible pulse oximeter can measure blood oxygen levels and pulse waves with high accuracy. The devices are also stable in air, with long-term operational life and minimal degradation after repeated stretching tests. The study highlights the potential of organic optoelectronic devices for biomedical applications, including health monitoring and non-invasive sensing. The research provides a practical solution for integrating electronic functions onto the skin, enabling the development of smart wearable and medical systems.Researchers have developed ultraflexible organic photonic skin, which integrates electronic components onto the skin to enable health monitoring and information technologies. The system includes three-color, highly efficient polymer light-emitting diodes (PLEDs) and organic photodetectors (OPDs) that are ultraflexible and conformable, with a total thickness of only 3 micrometers, thinner than the epidermal layer of human skin. These devices can be laminated onto the skin to create optoelectronic skins (oe-skins) that provide multiple electronic functions such as sensing and displays. The ultraflexible reflective pulse oximeter, made by integrating green and red PLEDs with OPDs, can unobtrusively measure blood oxygen levels when applied to a finger. On-skin seven-segment digital displays and color indicators can visualize data directly on the body. The study demonstrates the feasibility of electronic functionalization of human skin using ultrathin devices. The devices are fabricated on 1-micrometer-thick polymeric films and laminated onto curved surfaces. The passivation layer, composed of alternating inorganic (SiON) and organic (Parylene) layers, ensures the devices can operate in ambient conditions. The ultraflexible PLEDs and OPDs exhibit high performance, with excellent electrical characteristics and mechanical flexibility. The PLEDs have high external quantum efficiency and luminance, while the OPDs show good light sensitivity and stability. The devices are highly flexible and can withstand extreme stretching and bending, making them suitable for wearable and medical applications. The ultraflexible pulse oximeter can measure blood oxygen levels and pulse waves with high accuracy. The devices are also stable in air, with long-term operational life and minimal degradation after repeated stretching tests. The study highlights the potential of organic optoelectronic devices for biomedical applications, including health monitoring and non-invasive sensing. The research provides a practical solution for integrating electronic functions onto the skin, enabling the development of smart wearable and medical systems.