Two-dimensional transition metal dichalcogenides (2D TMDs) ï¿½ whose generalized formula is MX2, where M is a transition metal of groups 4ï¿½7 and X is a chalcogen ï¿½ exhibit versatile chemistry and consist of a family of over 40 compounds that range from complex metals to semiconductors to insulator. Complex metal TMDs assume the 1T phase where the transition metal atom coordination is octahedral. The 2H phase is stable in semiconducting TMDs where the coordination of metal atoms is trigonal prismatic. We have been studying the 1T phase in semiconducting TMDs. In particular, we have focused on mechanisms involved in inducing the meta-stable 1T phase, kinetics of phase transformation and fundamental structural and electronic properties. We have implemented phase-engineered materials as hydrogen evolution reaction (HER) catalysts and as low resistance contact electrodes in electronic devices. We have also exploited the metallic nature of the 1T phase to functionalize a variety of TMDs. The attachment of functional groups leads to dramatic changes in the opto-electronic properties of the material.