Juvenile idiopathic arthritis, Cytokines, Lymphocytic subset, Biologic drugs, Treat-to-target Juvenile idiopathic arthritis is the most frequent rheumatic disease in childhood. Its diagnosis is still clinical and recently new classification criteria have been proposed. Over the past twenty years, there have been significant improvement in understanding the pathogenetic mechanisms leading to the implementation of targeted therapies. Indeed, the introduction of biological drugs has changed the quality of life of these children, with a rapid control of the disease activity and a reduction in the complications related to the disease and to the use of steroids, which is today very limited. The way of evaluating patients has also changed: joint ultrasound has become a fundamental tool of the daily practice of the paediatric rheumatologists. This article aims to highlight the new discoveries that have changed the management and prognosis of patients affected by juvenile idiopathic arthritis.