This chapter introduces the role of the interface in a myriad of applications, including emerging and rapidly expanding fields such as microsystems and nanosystems. Interfacial science and technology deal with the behaviors of fine-particle dispersions, fibers and thin films, and other systems strongly influenced by the properties of their interfaces. A few of their applications with relevance to problems of public health and welfare directly affecting modern societal needs, such as energy storage and generation, environmental techniques, biomedical, cosmetics, electromagnetic interference shielding, transparent electrode, sensing, and actuation are discussed.