Technical Core Summary The Technical Core will provide general infrastructure and tools to address technical challenges in adopting mobile approaches to research including: participant recruitment, retention, and support; validating and understanding new cognitive and non-cognitive tests and other physiological and environmental data; and securing data appropriately in the context of significant participant privacy concerns. Under the original Mobile Toolbox (MTB1) grant, we successfully built and deployed a system that allows researchers to select from a library of validated measures, design a virtual study protocol that delivers these measures to participants through an app running natively on their iOS or Android smartphone, and retrieve aggregated participant data through web or programmatic interfaces. Our goal for the MTB platform is to provide a complete end-to-end solution for the use of remotely administered cognitive and other non-cognitive measures by researcher teams. We will achieve our overall goal to support the continued expansion and dissemination of remote mobile measures through two aims: Aim 1: We will continuously expand the MTB library of remote, self-administered measures; Aim 2: We will provide continued support and maintenance of the Mobile Toolbox platform and extend its capabilities to make it increasingly easy for researchers to manage virtual interactions with study participants to improve recruitment and adherence. We will focus on expansion into non-cognitive domains including contextual factors, and psychological, physical, and behavioral functions, as well as the inclusion of passive sensor data streams to provide deeper context for already validated measures. We will also streamline the communication between study managers and remote participants, include support for custom survey questions to be delivered through the MTB app, and adopt best practices on engagement for future study design. We will keep hardware and software up to date and ensure continued reliability, performance, and security of the platform.