This work presents some fundamental features of pyramidal site-controlled In GaAs Quantum Dots (QDs) grown by metal-organic vapour phase epitaxy on patterned GaAs (111)B substrate. The dots self-form inside pyramidal recesses patterned on the wafer via pre-growth processing. The major advantage of this growth technique is the control it provides over the dot nucleation position and the dimensions of the confined structures onto the substrate. The fundamental steps of substrate patterning and the QD formation mechanism are described together with a discussion of the structural particulars. The post-growth processes, including surface etching and substrate removal, which are required to facilitate optical characterization, are discussed. With this approach extremely high uniformity and record spectral purity are both achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim