Some embodiments include formation of at least one cavity in a first semiconductor material, followed by epitaxially growing a second semiconductor material over the first semiconductor material and bridging across the at least one cavity. The cavity may be left open, or material may be provided within the cavity. The material provided within the cavity may be suitable for forming, for example, one or more of electromagnetic radiation interaction components, transistor gates, insulative structures, and coolant structures. Some embodiments include one or more of transistor devices, electromagnetic radiation interaction components, transistor devices, coolant structures, insulative structures and gas reservoirs.