User-expandable packaging

A packaging material web stock, comprising:

• a plurality of adjoined packaging units arranged longitudinally in a series, each of the packaging units comprising:
• a plurality of walls overlaid with each other to define an inter-wall cavity therebetween that is configured to house an object to be shipped, and
• a plurality of inter-wall seals configured to seal the walls to each other and including a plurality of transverse inter-wall seals that extend transversely across the walls of a respective one of the packing units and are located at a first and a second longitudinal end of the respective packaging unit, wherein each of the walls comprises:
• first and second plies overlaid and sealed to each other at a plurality of inter-ply seals that include a plurality of transverse inter-ply seals extending transversely across the plies, wherein an inter-ply cavity is defined between the overlayed plies and the transverse inter-wall seals of the respective packaging units;
• and
• an expansion material disposed in the inter-ply cavities in an unexpanded configuration, the expansion material having a composition to expand into an expanded configuration upon application of expanding conditions, wherein the expansion material is arranged within the interior inter-ply cavities such that when expanded to the expanded configuration the expansion material is configured to provide cushioning in the walls to the object to be shipped.