Chronic airway diseases, such as asthma, bronchiectasis and chronic obstructive pulmonary disease (COPD), are complex and heterogeneous conditions. Hence, their assessment and management need to be personalized and precise. A decade ago, a precision medicine strategy based on the presence of treatable traits was proposed. This proposal generated a lot of interest and publications. This issue of Respiratory Medicine is fully dedicated to this topic. In this first introductory chapter, we present the reasons that underlie it (“Why”), outline its core content (“What”) and discuss how to implement it in clinical practice (“How”).