An expert overview of common congenital differences affecting the thumb and opportunity for real case discussion with experienced congenital hand surgeons. In addition to gaining in-depth knowledge and practical tips regarding decision-making and the clinical management of these complex cases, we will show how the clinical presentation relates to the underlying basic science: Through presenting emerging evidence that radial polydactyly and thumb hypoplasia are part of one spectrum embryologically, we will demonstrate how an appreciation for the underlying embryology and anatomy can lead to improved management of these children.