With well over 300 stores in 38 countries, Ikea is – by miles – the largest furniture retailer in the world.

What that means, of course, is that thousands and thousands of homes across the globe are choc-a-block with Billy bookcases and Malm dressers and Lack tables. But insanely popular as the above are (and they really, really are), they are not Ikea's best ever product. Not according to the company's design manager, anyway. Marcus Engman has been working with Ikea since he was 16. In the late 1970s, Engman father, Lars, who also worked for the Swedish furniture giant, designed a sofa that we today probably would call iconic. So while Engman might be slightly biased, of course, he sat down with Business Insider and spoke of why he thinks the Klippan is the best Ikea product of all time. His main reason? It is compact enough to fit easily through most house doorways, and can easily be transformed through its interchangeable fabric covers. "It's a sofa that evolves with you," Engman explains. “You can change its colour and live with it for a long time. I still remember when he brought it home for tests, and he asked me and my sister what we thought of it." The Klippan, like most things, have seen some changes in over the year since 1979, when it was designed. While the original featured a wooden frame, the more recent versions are made with more lightweight materials in particleboard, polyurethane foam, and fiberboard. The legs were previously also wooden, but are now made of aluminium. In 2004, its parts were redesigned in order to make it possible to flat pack and assemble at home. “I have a lot of fond memories with that sofa," Engman admits. "I’m glad it has survived for so long."