Since the 1990s, printable, transparent, and low-voltage transistors have attracted great attention from academia and industry due to the demand for specialized circuitry such as in radio-frequency identification (RFID) tags, medical sensors, and electronically active textiles. Some flexible and portable devices have been available commercially; however, the challenge to convert more conceptual devices into real-life applications is still the materials. This article starts with a brief summary of some examples from silicon electronics, to place the other materials in context, followed by the topics including high-capacitance dielectrics, transparent conductors and semiconductors, and printability of recently developed electronic materials. The recent progress about these topics is reviewed, and discussions of each topic suggest future science and engineering research opportunities.