The best-known toy brick maker is the LEGO company, which is based in Billund, Denmark (as of November 2026). It began in 1932 as a small carpenter's shop in the village of Billund, and before plastic bricks it made stepladders, ironing boards and wooden toys. Its name comes from two Danish words, leg godt, which mean play well, and the company registered the name as a trademark in Denmark in 1954. Yet the idea of a studded plastic brick did not start in Billund. Hilary Page, an English toy designer, patented hollow interlocking plastic bricks with 4 and 8 studs, and he founded his own company, Kiddicraft, in 1932; that British company sold interlocking plastic bricks with studs before LEGO did.

LEGO acquired a plastic injection-molding machine in 1947, the first in Denmark, and began making Automatic Binding Bricks two years later. Sales of the plastic toys were mediocre in the early 1950s, and the first plastic bricks had no tubes inside, so they did not hold together as well as later ones. Even in 1958 the bricks were hollow underneath, so models were wobbly and customers complained. The man who thought of the tubes was Godtfred Kirk Christiansen, the founder's son. He sketched several fixes, including tubes, at a meeting on January 23, 1958, and the patent was filed five days later; the tubes make the bricks grip each other, which LEGO calls clutch power.

Toy bricks stick together because the studs on top fit tightly between the tubes inside another brick. A brick one stud wide has no room for a tube, so it has a thin bar that the studs squeeze slightly; clutch power is the force needed to pull two bricks apart, measured in newtons, and LEGO keeps the exact ideal number secret. With the stud-and-tube design, six 2x4 bricks can be combined in 915,103,765 different ways, according to LEGO. The company has not changed the brick's basic connection since 1958, so a new brick still fits an old one. The DUPLO brick for toddlers, which was invented in 1967, fits standard LEGO bricks.

The plastic matters as much as the shape. ABS is a mix of three ingredients, acrylonitrile, butadiene and styrene and was first made in the late 1940s, then sold commercially in the 1950s. ABS is a thermoplastic, so it softens when heated and can be shaped in a mold and cooled hard again. It is also a tough, strong plastic that can survive being dropped, which suits a toy. Engineers at the Open University tested a 2x2 ABS brick in a hydraulic testing machine until it failed, and the average brick took about 432 kg (950 lb) before it deformed. Since one brick has a mass of 1.152 g, that equals a tower of about 375,000 bricks, roughly 3.5 km high.

LEGO changed from the wood-based cellulose acetate to ABS in 1963 because ABS was more stable and held color better. ABS is cheap, takes any color and can have a glossy finish, and one history of LEGO lists it as heat-resistant and resistant to many acids. Plastic was chosen for toys partly because it is easy to clean and comes in many colors and shapes. Raw ABS is naturally translucent, which means it lets some light through, and its ivory to white tone is why pigments are added to color it. At LEGO the color for specific bricks is added at the molding machine, so one stock of granules can make every color.

Now follow the plastic into the factory, where the brick takes its shape. Toy bricks are made from tiny plastic granules, stored in giant silos and sent to the machines through tubes. Machines melt the plastic and squeeze it into a mold shaped like the brick. Hot plastic is injected into one side of the mold, spreads through little channels and fills the brick-shaped space. Cold water flows through the mold to cool the plastic, and then the mold opens and the new bricks drop onto a belt. Leftover plastic from the mold is ground up and used again almost right away. At the big Billund plant in 2008, the silos fed the molding machines about 60 tons of plastic granules every 24 hours.

Checking quality takes careful counting, and the last steps finish each piece. Bricks that have faces or patterns get them printed or stamped on by machines, and decorating is the most expensive part of making a LEGO piece. Pieces for sets are put into small bags, and the bags go into boxes that machines close. Machines count the pieces that go into each box using light sensors. A 2011 factory tour found that a bag of bricks had to weigh between 94.9 and 95.7 grams, and a screen showed 5,354 bags in the target range and six outside it. Any box or bag that is too light or too heavy is flagged so a person can check it.

A factory also has to deal with waste. In 2011, a visit found that almost all the plastic in a LEGO factory was reused: scrap from the molds is ground up and fed back in. Faulty pieces and the clear plastic used to flush a machine between colors were ground up and sold on. Even so, plastic that is thrown away does not rot away like food or paper, and it can stay around for hundreds of years. Plastic made in the world grew from about two million tonnes in 1950 to more than 400 million tonnes a year today (2026). Many plastic things, such as bottles and takeout boxes, are made to be used once and thrown out.

Most LEGO bricks are made of ABS, an oil-based plastic, and LEGO says it is looking for other materials to use instead (as of November 2026). It announced in 2020 that it would use recyclable paper bags, and its sustainability pages report that more than half of the packing lines (56 percent) have switched. Not every new material worked, however; by 2023 LEGO had tested more than 300 different materials, and some worked better than others. A recycled-bottle brick prototype was dropped in 2023 after two years of testing because it would not reduce carbon emissions. Bricks, by contrast, are built to be taken apart and built again, and new bricks still fit bricks made since 1958.

Words to know

• interlocking: fitting together
• trademark: protected name
• translucent: lets light through
• pigments: color powders
• deformed: changed shape