Normally the molecules can only assemble in a chain. They can make solids in three dimensions by being long and making a big tangled mess. It's like extruding dough into spaghetti, then stirring it around to make a big tangled ball. Instead, they found a way to roll the dough out into an arbitrarily large flat lasagna-like noodle. Then they stacked them and found they stick to each other well and could make a much stronger material than the spaghetti ball. The only real limit being the amount of dough and a space to roll it out on.