Two models for the 30 nm fibre that have been proposed are the ellipsoid model and the solenoid model. These are potential packing structures to condense the 10 nm fibre into the 30 nm fibre.
The ellipsoid model is a coiled structure of DNA.
The zig-zag model described the 30 nm fibre adopting a double helical spiral, with proteins linking between two strands of DNA to provide structure.
To form these structures, linker histones (H1) are required to allow nucleosomes to join together.
It is not known which structure the 30 nm fibre adopts, although both the ellipsoid and zig-zag models are deemed to be plausible.