This webinar explores how longitudinal data can support evidence-based policymaking, public communication, and advocacy by NGOs and journalists. Using a life-course perspective, it demonstrates why social phenomena such as inequality, health, education, and wellbeing can only be fully understood by following individuals and cohorts over time rather than relying on cross-sectional snapshots. The presentation introduces key types of longitudinal data in Europe, including panel studies, cohort studies, and linked administrative data, and discusses their strengths for analysing trajectories, identifying early divergence, and evaluating policy interventions. Through a case study on childhood socioeconomic conditions and frailty in older age, the webinar illustrates how early-life disadvantage accumulates across the life course and shapes long-term health outcomes. The session also provides practical guidance on accessing major European longitudinal datasets (e.g. SHARE, GGS, ESS) and on effectively communicating longitudinal findings to different audiences, including policymakers, NGOs, journalists, and educators. The webinar is intended for users interested in applying longitudinal evidence to policy, communication, and social impact work.