This project focuses on the use of plasmonics in manipulating light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved optical microscope resolution. The presented work fills some of the gaps in the current knowledge of plasmon waveguides and develops two new types of nano-focusing structures for sensing and microscopy. These nano-focusing structures focus light to a nano-scale region and may prove easier to implement than previous structures. While the investigation of plasmon waveguides, capable of guiding the plasmon on the nano-scale, has provided a greater understanding of the guided plasmons and may result in new applications e.g. a sub- wavelength coupler has also been investigated in this thesis. The methods used in these investigations were the geometric optics approximation, effective medium method, finite- difference time-domain and the software package COMSOL. Dr. Vernon’s work was performed at QUT and the University of California Berkeley.