Nanite is Unreal Engine 5's virtualized geometry system. Instead of authoring a chain of progressively simpler LOD meshes by hand, you import the full-detail source and the engine streams whatever level of detail the current view needs.
For artists this removed a tedious step and raised the ceiling on visual density. For source control it changed the size distribution of a project completely. A hero asset that would have shipped as a 40 MB optimized mesh in UE4 now carries its full source geometry and routinely lands in the hundreds of megabytes, sometimes into the gigabytes.
Nanite is not the only contributor. Lumen removed baked lightmaps but encouraged higher-quality source material to light. Virtual textures made 8K and 16K inputs practical where they would previously have been downsampled on principle. MetaHuman characters arrive with dense meshes, groom data, and multi-gigabyte texture sets. The combined effect is that Unreal Engine 5 projects outgrew the storage assumptions most version control pricing was built around.
This is where teams on metered plans discover their storage tier, usually a couple of months into production. On USourceControl storage and bandwidth are unlimited on every plan including Free, with a 5 GB ceiling per individual file.