Collectively oscillating electrons—plasmon—within propitiously designed nano-objects create locally enhanced optical field, thus boosting light-matter interaction in their vicinity. As a result, this unique characteristic significantly amplifies normally weak optical responses. This talk presents two of my research efforts on this subject. Firstly, a new-generation near-field optical microscopy will be introduced: utilizing a photo-excited tip as the light bulb to probe the optical response in proximity of the tip apex, named as scattering-type scanning near-field optical microscope (s-SNOM). Secondly, a high-speed diagnosis platform for water analysis, food safety, and microbiology based on surface-enhanced Raman scattering (SERS) with the use of a array of these “light bulbs” will be presented. In the context of applied mathematics, this talk will illustrate some successful examples how mathematical modeling, numerical calculation and statistics further the development of this vastly developing field. Finally, the talk concludes with the pressing challenges and future opportunities of this field and how applied mathematics can help address those issues.