Toy giant Lego is aiming to put bricks made from recycled drinks bottles on shelves within two years.
Lego makes about 3,500 different bricks and shapes, but faces the challenge of coming up with a sustainable product that can last years - decades, even.
The goal is to find a product good enough that people don't notice the difference, said Lego's Tim Brooks.
He did not specify how many of its bricks will contain recycled material, adding: "It's too soon to say."
But he added that Lego wants to start using the bottle-made ones "as soon as possible".
Mr Brooks, Lego's vice president of sustainability, said the two types of blocks should fit together and be interchangeable like any Lego product.
Lego said that many customers, both children and adult, were asking for more sustainability when buying products in general, and had contacted the firm to say so.
But Friends of the Earth plastics campaigner Camilla Zerr said that "it's really important that recycling isn't hailed as the default solution to the plastics crisis."
"Manufacturers must ensure toys are made to endure many years of use, so they can be handed down and reused from generation to generation," she adds.
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Lego plans to sell bricks from recycled bottles in two years
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