When Kim Min-seok gave the go-ahead in June 2016 to publish a 90-second clip of a children's song, he had no idea what he was unleashing.

It became a global phenomenon, clocking up more than 16 billion views - YouTube's most watched video ever.

That song was the incredibly catchy Baby Shark.

Not only has it captivated toddlers and terrorised adults around the world, it laid the foundations for its creator Pinkfong to become a media business worth hundreds of millions of dollars.

“We didn’t expect it to stand out from our other content," Mr Kim, Pinkfong's chief executive, told the BBC from the firm's headquarters in Seoul.

"But looking back, it became a major turning point that set the stage for our global journey.”

On Tuesday, that journey took Pinkfong to the South Korean stock market, where its shares rose by more than 9% on their debut, giving it a valuation of more than $400m (£304m).

Founded in 2010 as SmartStudy, the firm made digital content for children up to 12 years of age.

It had just three employees, including Mr Kim and the firm's chief technology officer, Dongwoo Son.

"The office was tiny - even smaller than this," recalled Mr Kim, gesturing to the conference room he was calling from.

It was so small "we didn't even expect a salary at the time", he........

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