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Helfrich et al. (pp. 2387–2401) have prepared and investigated site-selective InAs quantum dots (QDs) on pre-patterned GaAs substrates in order to gain further understanding of the mechanisms controlling the structure and the distribution of site-selective QDs. Regular arrays with multiple QDs (upper left image on the cover) or individual QDs at pre-defined locations (upper right) are of interest, depending on the envisaged applications. Besides geometrical parameters of the pattern and growth parameters that determine the final QD structure to some extent, a post growth treatment based on in situ annealing has allowed to manipulate the size of the QDs as well as the number of QDs per site in an array (lower left). Further insight was gained by analyzing a single array of site-selective QDs grown inside nanoholes with X-ray diffraction techniques. The structure and the periodicity of the holes is revealed in the measurement and can be modeled using finite element method (lower right). A proper understanding of the contributions from hole shape and pattern is essential in order to further investigate the ordering of QDs nucleating inside regularly spaced holes.