Computer chip producer Nvidia is now the world's most valuable company - overtaking Apple and Microsoft.
Shares climbed 3.5 percent on Tuesday, making it worth $3.35 trillion (USD).
The surge is driven by optimism about its AI technology.
Sharesies co-founder, Leighton Roberts, says he can't predict whether it will fall as quickly as it's risen.
He says it's hard to judge, but believes a lot of excitement is still to come.
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