Our brain evolved in a manner to enable itself to modify its structure depending on its environment. The thalamus is a large sensory relay station and it is closely integrated into the cortical circuits. Thalamic projections are responsible for dispatching most of the information to the cortex from the sensory periphery from early stages throughout life. The earliest inputs to the cortex are capable of constituting an extrinsic signal that plays a part in triggering other changes in the establishing cortical circuitry, leading to some aspects of specific regional differentiation and a real specializations. Unravelling the mechanism by which developing thalamic axons interact with the forming cortical circuitry in their target regions is important in understanding how cortical organization is determined. This book intends to bring together systems and molecular approaches on various fundamental issues on thalamocortical development and plasticity. Functional cortical circuits cannot be appreciated without thalamocortical circuits and cortical development cannot be considered without thalamocortical pathway development. The 16 chapters address key questions with diversity of techniques; ranging from molecular genetics, in vitro and in vivo methods to classical anatomical, electrophysiological and imaging procedures. The conceptual approaches formulated in these chapters should be a rich source for future research in this area.