Lego is an idea as much as it is a toy; if you try hard enough, you can fit the entire story of the last century of child’s play and the hopes and desires of every parent into one of its 9.6-millimeter-tall rectangular plastic bricks. Molded in a thermoplastic polymer, acrylonitrile butadiene styrene, Legos are known for their durability, which is why you can pull out the 30-year-old Legos stashed in your parents’ basement and, dated color schemes aside, they’ll be the same as they ever were. Not only will they look the same, but they will fit together with every other one Lego has ever made, even those going back to 1949, when a Danish toy-maker named Ole Kirk Kristiansen made his first plastic brick. Lego calls it the System of Play, and it is both a manufacturing principle, allowing the company to reuse the same molds to make infinite new sets, and a play proposition: The more bricks you own, the more you can build. ... Like all 6,500 Lego elements — cubes, rectangles, octagons, wheel beds, arches, even the tiny semi-circular hands of yellow mini-figures — the standard brick has a variation of just 0.004 millimeters, which means Legos are more precisely crafted than your coffeemaker, your television, even your iPhone. ... By 2003, the company was on the brink of financial collapse, just three years after Fortune had named it “Toy of the Century.” ... In Lego lore, the crisis provoked a companywide soul search. And where the soul was located was in the brick. Henceforth, the brick would be the center of everything it did, toy trends be damned. ... play researchers argued that toys should foster more open-ended creativity and exploration — toys that forced the child to do the work, like Lego.