Type 1 diabetes (T1D) is caused by the auto-immune destruction of pancreatic cells and is characterised by absolute insulin insufficiency. The disease was thought to be the prevalent type of diabetes in children and adolescents, affecting up to 0.1% of the world population. T1D is a typical complex and heterogeneous pathology, occurred in genetically predisposing subjects as a result of harmful influence of non-genetic (environmental) factors. This book explores important research in this field.