Semiconductors have played an important role in the development of information and communications technology, solar cells, solid state lighting. Nanowires are considered as building blocks for the next generation electronics and optoelectronics. In this talk, Professor Jagadish will present the results on growth of nanowires, nanomembranes and microrings and their optical properties. Then he will discuss theoretical design and experimental results on optoelectronic devices. In particular, Professor Jagadish will discuss nanowire and micro-ring lasers and integration of nanowires and microrings. He will also present the results on polarization sensitive, broad bandwidth THz detectors operating at room temperature. Nanowire based energy devices such as solar cells and photoelectrochemical (PEC) water splitting will be discussed. Future prospects of the semiconductor nanostructures will be discussed.