Nanomaterials have found widespread use in many applications, including those related to photonics, electronics, catalysis, energy conversion, sensing, imaging, and biomedicine. Chemistry plays a central role in all these developments. For almost three decades, my group has been working diligently to develop chemical methods for synthesizing colloidal nanomaterials with well-controlled properties. In this talk, I will briefly discuss some of the most recent developments, with a focus on the rational, deterministic, and controllable synthesis of various types of nanomaterials for applications in catalysis, energy conversion, drug delivery, and cancer theranostics. At the end, I will also discuss how to scale up the synthesis without losing control to produce nanomaterials with the quality, quantity, and reproducibility needed for a systematic study of their fundamental properties as a function of size, shape, and internal twin structure, as well as for the exploration of industrial and translational applications.