Colloidal semiconductor nanocrystals are versatile nanomaterials, whose properties are determined by their size, shape (quantum dots and nanorods, nanosheets, nanowires), composition, and compositional profile (i.e., single component, gradient or homogeneous alloy, doped, heterostructured). Heterostructured semiconductor nanocrystals (hetero-NCs) are particularly attractive, since they allow the spatial localization of photogenerated charge carriers to be manipulated by controlling the band offsets between the materials that are combined at the heterointerface. This has a dramatic impact on several optoelectronic properties. Moreover, the colloidal nature of these nanomaterials allows one to take full advantage of nanoscale effects to combine size-, shape- and composition-dependent properties with easy surface manipulation and solution processing. These characteristics have turned colloidal semiconductor NCs and hetero-NCs into promising materials for a myriad of applications (e.g., LEDs, solar cells, catalysis, biomedical imaging, etc.), motivating extensive research into their synthesis and optoelectronic properties. In our group, we have applied a multistage preparation strategy that allows the combination of different synthesis techniques in a sequential manner in order to achieve the targeted preparation of colloidal nanocrystals. This has allowed us to systematically investigate the optical properties of a variety of nanocrystal and hetero-nanocrystal compositions. In this seminar, I will discuss a selection of examples, chosen in order to illustrate specific synthesis strategies, as well as to show that composition, size, and shape control can be used to tailor nanoscale excitons, and consequently the optical properties of colloidal nanocrystals.