Mark Zuckerberg sat on a four-inch booster cushion as he was grilled by US senators over Facebook’s data scandal.
The firm’s CEO gave evidence in Congress after it emerged 87 million of the site’s users had their profile information accessed by marketing company Cambridge Analytica.
But it was his chair which caught the attention of people around the world, with photographs of the booster cushion shared widely on social media.
The thick cushion, the same shade of black as the chair, gave the 5ft 7ins billionaire a boost in height behind an ornate wooden desk.
One person wrote: "Is that a billionaire's version of a booster seat?"
Another Twitter user posted: "Wonder if they gave him crayons and a coloring book also."
In his opening testimony, he said that his company has taken several steps to restrict outsiders' access to people's personal information on Facebook.
Mr Zuckerberg said the firm is also investigating every app that had access to a large amount of information before the company moved to prevent such access in 2014 - something that came too late in the Cambridge Analytica case.
Mark Zuckerberg at Facebook Congress Hearing - In pictures
Facebook is under fire in the worst privacy crisis in its history after it was revealed that the Trump-affiliated data mining firm improperly accessed information from 87 million users – including over a million in the UK - to try to influence elections.
Mr Zuckerberg, 33, told Congress no-one at Facebook's app review team had been fired as a result of the Cambridge Analytica scandal.
“We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I'm sorry," Mr Zuckerberg said at the hearing.
He agreed the firm should take a "more proactive view in policing the ecosystem". But asked if Facebook should face tougher regulations, he replied that should only happen if they are the “right regulations”.
Barcelona footballer Lionel Messi is just under 5ft 7ins, and Hollywood star Tom Cruise is also 5ft 7ins.
