Plasmonics has become a very vibrant research area in nano optics. It allows us to concentrate, guide, and manipulate light at the deep subwavelength scale, promising enhanced light-matter interaction, next-generation optical circuits, sub-diffraction-limited imaging, and ultrasensitive biomedical detection. Furthermore, the assembly of rationally designed metallic structures can be used to construct metamaterials and metasurfaces with exotic properties and functionalities, including anomalous refraction/reflection, strong chirality and invisibility cloak. There is a pressing need of tunability and reconfigurability for plasmonics and metamaterials, in order to perform distinct functionalities and miniaturize the device footprint. In this talk, I will present our recent work in tunable and reconfigurable plasmonics and metamaterials. First, I will discuss the first demonstration of reconfigurable plasmonic lenses operating in microfluidic environment, which can dynamically diverge, collimate and focus surface plasmons. Second, I will present a designer metasurface that can efficiently control the polarization of Smith-Purcell emission of moving charged particle by coupling the inherent electric and magnetic dipoles of the metasurface. Finally, I will discuss origami-based, dual-band chiral metasurfaces at microwave frequencies. The flexibility in folding the metasurface provides another degree of freedom for geometry control in the third dimension, which induces strong chirality from the initial, 2D achiral structure. These results open a new avenue towards lightweight reconfigurable meta-devices.