Chemistry and physics share tremendous potential at the nanoscale. This is where chemistry excels and where physics predicts that many properties can be tuned. For example, charging properties, spins, phonons, and plasmons show pronounced effects in this regime. We investigate these fundamental states in nanocrystal quantum dots created by colloidal synthetic chemistry. Alongside basic studies utilizing optical spectroscopies, electrochemistry and transport measurements, we also integrate nanocrystals into optoelectronic devices for applications in infrared imaging and light emission. Our research is motivated by physical concepts and enabled by advances in chemical synthesis.