Why did chip-maker Nvidia's profits soar and is it living in a tech bubble?

The stock market darling on everyone's lips is Nvidia, which makes the processing chips that power everything from home computers to industrial machinery to cutting-edge artificial intelligence technology. On Thursday, the company stunned Wall Street with results that blew the roof off analysts' expectations, reporting $13.5bn in quarterly profits, $2bn higher than pundits had predicted. Its performance is being driven in particular by the AI boom, which has tripled the value of its shares this year and given it a market value of more than $1tn. California-based Nvidia is one of just five companies to have reached that milestone – along with Apple, Amazon, Microsoft and Google's owner, Alphabet – and the only one that isn't a household name. So why are its chips so hot, and what does the future hold?