Nanite

Nanite is a runtime, dynamic level-of-detail (LOD) system for 3D models. It is used in Unreal Engine 5 and is described as a "virtualized micropolygon geometry system". It is considered to be "virtualized", because it provides a virtualized representation of the geometry to the rendering system, even though it may load and stream parts of the model as needed - akin to the way virtual memory works.