A central question in plant biology is how plant cells can expand while maintaining a strong cell wall. Two main mechanisms have been proposed for irreversible wall expansion, intussusception and chemorheological growth. We discuss here the molecular nature of the cross-links and how their removal can contribute to growth of both tip-growing or diffusely-growing cells. We also discuss recent observations suggesting that at least in some cases processive intussusception may contribute to cell wall expansion in plants.