Morphoea, also known as localized scleroderma, is a debilitating fibrosing disorder of uncertain aetiology, affecting the skin and subcutaneous tissues. Paediatric-onset disease is not uncommon and is associated with frequent relapses. The disease has complex pathogenetic mechanisms and multiple clinical subtypes, and affects children of all ages. Recent research has focused on elucidating the disease pathophysiology and identifying measures of disease activity. We performed a literature search on PubMed, MEDLINE and Google Scholar, using keywords such as 'pediatric morphea', 'juvenile localised scleroderma' and 'juvenile systemic sclerosis'. Relevant studies, including randomized trials, reviews of standard current guidelines and original research articles, were selected, and results were analysed before being summarized. In the first of this two-part review, we provide a bird's-eye view of the current literature concerning the epidemiology, aetiopathogenesis and clinical classification of paediatric morphoea; in Part 2, we review the diagnosis, markers of disease activity, management and natural history.