We present an overall impression of the present state of knowledge on the formation, via a modified Stranski-Krastanov growth mode, of InAs quantum dots (QDs) on GaAs substrates. We will begin with the substrate orientation and surface reconstruction specificity of QD formation, which demonstrates that QDs are the exception rather than the rule in this system, with the implication that a second process, in addition to strain relaxation, is involved in the driving force. We then discuss the formation of an alloy wetting layer, and although it may not be unique to growth on the GaAs(001) c(4 × 4) surface, it is very much more marked than on any other. This is an important effect, in that QD formation is effectively limited to the same surface reconstruction. The next stage involves this formation process and we will review the experimental evidence, including dot composition, size (volume) distribution (including scaling behaviour), and two-dimensional to three-dimensional transition effects, with some comments on possible experimental artefacts in this area. We conclude with some comments on QD shape, based mainly on reflection high energy electron diffraction (RHEED) results, but including a comparison with results from transmission electron microscopy (TEM) and scanning tunnelling microscopy (STM).