 Adolescents are particularly vulnerable to tobacco initiation and escalation due to their lack of experience and maturity. Exposure to tobacco industry promotions and secondhand smoke increases the likelihood of tobacco use, while support for smoke-free air policies reduces it. Additionally, sex, region, and income moderate the effects of these factors, resulting in higher rates of susceptibility and use in males in high-income countries, Africa and the Americas, and Europe and Southeast Asia respectively. This article was authored by Naon Kim, Wayne Lowe, and Danielle E. McCarthy.