Textile electronics refer to the fibers or fiber assemblies (yarn, fabric, or clothing) possessing electronic functions, including generation, transmittance, evaluation, and modulation of electrons. It includes devices and systems. Since textile electronics are light, flexible, breathable, and functional, it exhibits great potentials in a wide range of applications. However, the noticeable progress of textile electronics has been focused on large-area, flexible devices with several functions, such as sensation, actuation, display, antenna, and energy harvesting and storage. The current textile electronic system is achieved by hybrids of microelectronic chips and textile electronic devices. They corporate together to provide complicated functions of sensation, actuation, communication, analysis, control, learning, memory, and adaption. The textile electronic system is an important branch of wearable electronics. This article provides a comprehensive review and analysis of textile electronic devices, electronic system integration, and applications. Firstly, it focuses on the development and technology of a number of textile electronic devices, which include sensors, actuators, displays, antennas, energy storage, and generators. This section introduces the functions, classification, performance, and limitations of textile electronic devices. In the textile electronic system, the signal module, microprocessor, data storage, and communication module now cannot be realized on textile due to the technology limitation. Therefore, it is necessary to incorporate the relevant microelectronic chips and micro-electro-mechanic devices into the textile to achieve system-on-fabric. The next section of this review describes and analyzes the research gaps of textile electronics in wearable applications. The key requirement is that textile electronics should deliver advanced electronic functions without deteriorating the textile properties. In addition, textile electronics also need to face strict requirements on biocompatibility, laundering, and comfortability. We then elaborate on the major scientific issues in several dimensions, covering design, synthesis, characterization of flexible electronic materials, multi-physics and multi-scale modeling of textile electronics devices and systems, test standardization of textile electronic devices and systems, and safety issues of textile electronics. Then, we discuss the present core technologies of textile electronics in various aspects. The electronic materials include intrinsic conductive materials that include metal in different dimensions, conductive and semiconducting polymer, and carbon derivatives. The additive fabrication technology covers printing techniques, coating, physical vapor deposition, chemical vapor deposition, in situ polymerization, carbonization, and others. At the device level, the fabrication technology can be separated into single multicomponent fiber electronics, or fiber assemblies, or heterogeneous assembly of microelectronic chips in the textile structure, elaborated with examples. In addition, we discuss different connection integration methods, such as embroidery, weaving, and knitting. We also discuss the software development for textile electronics, optical fiber system requirements, and test standards for textile electronics. The last section elaborates on potential applications of textile electronics. In online healthcare and individualized medical treatments, textile electronics provide real-time monitoring and wireless feedback of human physiological and physical signals, such as temperature, electrocardiogram (ECG), electromyography (EMG), respiration, gait, posture, etc. or provide intervention and treatments. It breaks down the geographic limitation …