Atrial fibrillation (AF) is the most common sustained arrhythmia and its treatment continues to be a challenge. Recently, delayed enhancement (DE)-MRI was introduced in the diagnosis and treatment of AF by the assessment of atrial fibrosis, which is considered the hallmark of the arrhythmogenic substrate in AF. Atrial fibrosis was reported to be an independent predictor of arrhythmia recurrences. Post-ablation DE-MRI allows for assessment of the total scar burden, complete encirclement of pulmonary veins, and the assessment of residual fibrosis, which were all reported to be strong predictors of arrhythmia recurrences post-ablation. Current pathophysiological perspectives for AF are heavily based on the adagium AF begets AF. However, several recent observations, such as atrial fibrosis being present in non-AF patients, do introduce a new pathophysiological perspective for AF. Potentially, atrial fibrosis is a disease process that triggers the initiation and maintenance of the syndrome AF.