Nanocomposites represent an interesting class of materials because their applications are of multidisciplinary importance. Herein, interactions at the interface of heterostructures, leading to superior performance and sometimes to synergistic interactions, are highlighted. Although the types of junctions seem to be similar in different fields, the requirements for their function is device-dependent and thus no generally valid recipe can be utilized. Nonetheless, the overlap between research fields unveils the unique opportunity to combine the different knowledge and expertise as an inspiration to designing new composites for photoelectrochemical water splitting, photocatalysis, chemoresistive sensors, batteries, and composite multiferroics. A non-comprehensive overview is provided with focus on selected examples to highlight the concepts behind these nanojunctions.