This Notice of Funding Opportunity (NOFO) encourages foundational research projects that seek to refine and test valid methods for characterizing preteen suicide risk and protective factors across multiple domains and for operationalizing suicide thoughts and behavior (STBs) and nonsuicidal self-injury (NSSI) among preteen youth (ages 8-12). An emphasis is placed on the inclusion of sub-populations of youth that experience health disparities and may have been underrepresented in prior youth suicide research. Studies may focus on developing new or adapted developmentally and culturally appropriate methods for assessing and characterizing risk and protective factors, examining the acceptability and utility of existing assessment methods, evaluating the relevance of risk and protective factors for diverse preteen youth and their families, modeling risk-factor trajectories, and refining sampling strategies. The research projects funded through this announcement will participate in a research consortium with other R01 recipients to share and analyze data, recommend candidate measures that will be included as common data elements in future research and practice contexts, identify optimal approaches for sampling individuals from underrepresented backgrounds, and disseminate project findings. In addition, each research site will work with the Data Coordinating Center (supported by RFA-MH-24-322) to facilitate data sharing and harmonization.