TWKB (Tiny WKB) can be aggregated and nested. The result is a special type. Since the TWKB-geometry holds it’s own ID (like many text-based gis-formats) , the result of an aggregation of many TWKB-geometries also nests the ID’s into the new aggregated TWKB geometry.
This gives us possibilities like creating a type of vector tiles on the fly. I have tried to demonstrate it here, but I didn’t get it as visual as I had hoped.
Those types is described as type 21-24 in the first draft of TWKB-specification.