Microsoft HoloLens is an augmented reality headset developed by Microsoft that allows users to interact with 3D holograms overlaid in their real-world environment. It uses sensors and a stereoscopic 3D display to map the user's environment and allow them to place and interact with holograms. Some key features include its cordless and untethered design, spatial sound, gesture controls, and ability to run Universal Windows Platform apps. Potential applications include remote assistance, education, design/visualization, and gaming. The device represents a new way for users to visualize and interact with digital content integrated into the physical world around them.