PROJECT SUMMARY – PROJECT 4 The tobacco product landscape changed drastically in the last decade with the proliferation of non-combustible tobacco products like e-cigarettes (ECs) and new oral nicotine pouches (ONPs). ECs are the most used tobacco product among adolescents and young adults (AYA) and ONP sales are climbing rapidly. The tobacco industry has a long history of manipulating three dimensions of nicotine (concentration, form, and isomer) to improve a product's sensory experience and nicotine delivery. Additionally, the industry has a history of creating a product graduation strategy whereby some products (defined along their nicotine dimensions) are “starter” for novice users and others are “robust” for longer-term users. Further, the tobacco industry pairs their products with specific marketing strategies designed to increase product appeal. The goal of Project 4 (P4) is to provide a comprehensive understanding of how industry strategies across the nicotine dimensions impact product perceptions, use behaviors, and dependence among AYA in the natural environment. Participants will be a national sample of recent initiators (within 6 months) of ECs and ONPs (N = 2000; ages 13-23). We will observe trends among these AYAs overall, and also among priority populations the tobacco industry has historically targeted including those who are lesbian, gay, bisexual, transgender, or queer (LGBTQ+), those with mental health disorders, and rural residents. Participants will be followed over a 2-year period; this prospective observational study will consist of surveys every 6 months, paired with 3 ecological momentary assessment (EMA) bursts, to characterize perceptions, use, and marketing exposures. Aim 1 will determine how ECs and ONPs are perceived over time and across nicotine dimensions in terms of liking, risk perceptions, and social acceptability. Aim 2 will identify patters of escalation in use of ECs and ONPs across the nicotine dimensions. Aim 3 will determine which nicotine dimensions are most predictive of nicotine dependence. P4 supports The Ohio State University's Tobacco Center for Regulatory Science overall integrative theme “Flipping the Script”: Using the Industry's Nicotine Playbook to Maximize Public Health by examining the impact of ECs and ONPs, defined by their nicotine characteristics and categorization as starter vs. robust, and perceptions of marketing in the real world. With strong ecological validity, P4 provides naturalistic observations of youth behavior to complement the controlled laboratory and experimental assessments that are used in P1-3. Integration across projects will directly inform premarket tobacco product applications and substantial equivalence reviews, modified risk tobacco product decisions, and product standards. P4 addresses FDA scientific domains of Addiction, Behaviors, and Marketing.