Phase 3, open-label study to assess the long-term safety and efficacy of liquid abrocitinib oral suspension with or without topical medications in children ≥2 years of age with moderate-to-severe atopic dermatitis (AD). This study will enroll participants in two cohorts: an extension cohort of participants who previously completed prior abrocitinib studies, and a de novo cohort of participants (6 to <12 years of age) who have not participated in previous abrocitinib studies. Study duration will be up to 2 years (or commercial availability, whichever occurs earlier). The study will enroll a maximum of approximately 500 participants with moderate-to-severe Atopic Dermatitis from study sites globally (extension cohort will enroll up to 320 participants; de novo cohort will enroll approximately 180 participants). All participants will receive the study intervention abrocitinib oral suspension.