Biology is curved, soft and elastic; silicon wafers are not. Semiconductor technologies that can bridge this gap in form and mechanics will create new opportunities in devices that require intimate integration with the human body. This talk describes the development of ideas for electronics that offer the performance of state-of-the-art, wafer-based systems but with the mechanical properties of a rubber band. We explain the underlying materials science and mechanics of these approaches, and illustrate their use in bio-integrated, ‘tissue-like’ electronics with unique capabilities in electrocorticography and cardiac electrophysiology, in both endocardial and epicardial modes. In vivo demonstrations with animal models illustrate the functionality offered by these technologies, and suggest several clinically relevant applications.