The development of novel therapies for chronic respiratory diseases has been limited by the lack of appropriate preclinical models. Now, Benam et al. have engineered a human lung-derived 'small airway-on-a-chip' that contains a differentiated, mucociliary bronchiolar epithelium composed of cells isolated from healthy subjects or individuals with chronic obstructive pulmonary disease (COPD), underlined by a functional microvascular endothelium. The chips accurately recapitulated the features of asthma, lung inflammation and COPD exacerbations, and chip responses to therapies were consistent with previous clinical findings.