Cardiomyopathies (CMPs) are myocardial disorders in which the heart muscle has structural and functional abnormalities in the absence of other causes sufficient to cause the disease. Until a few decades ago in medical literature, there was uncertainty and confusion about this entity. In the last years, advances in pathophysiology, pathology, biomarkers, genetics and molecular medicine, echocardiography, and cardiac magnetic resonance have brought light in the darkness. Since 1956 several definitions of CMPs have been adopted using terms as “inflammatory,”“non-coronary,”“myocardial disorders of unknown etiology”[1]. Classifications tried to make order in the complexity and, historically, were mainly based on phenotype [2, 3] missing multiple other aspects. In 2006 the American Heart Association proposed the definition of CMPs as follows:“cardiomyopathies are a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic. Cardiomyopathies either are confined to the heart or are part of generalized systemic disorders, often leading to cardiovascular death or progressive heart failure (HF) related disability”[4]. This classification is based on etiology, distinguishing CMP in genetic, acquired, and mixed, and splits CMPs into two groups, primary or secondary, as they involve predominately the heart or as a part of systemic disease. Brugada syndrome, long QT syndromes, short QT syndromes, catecholaminergic ventricular polymorphic tachycardia, and Asian sudden unexplained nocturnal deaths are put separately, but for the first time, channelopathies were mentioned in the classification of genetic cardiomyopathies. Two years later the European Society of Cardiology (ESC) chose a clinical and morphological classification (Fig. 1.1), reporting CMPs as “myocardial disorders in which structure and function of the myocardium are abnormal, in the absence of coronary artery disease, hypertension, valvular heart disease and congenital heart disease sufficient to cause the observed abnormality”. Dilated CMP, hypertrophic CMP, restrictive CMP, and arrhythmogenic right ventricular CMP are the four main specific phenotypes that have to be subsequently subclassified in familial and nonfamilial. Actually the picture is not so simple, with heterogeneity and overlapping forms [5].