Just born: Knut was born on December 5, 2006 in Berlin Zoo and spent his first weeks in an incubator after his mother Tosca rejected him.
At seven weeks, Knut was clearly starting to enjoy life.
His first public appearance on March 23, when he was three-and-a-half months old, was a global media event and the Knut show got started.
Here at four-and-a-half months: Fed a porridge of fish, catfood and vitamins, Knut thrived.
At five-and-a-half months, he had turned into a shaggy fighter.
Now, at six months, he's taking on the unmistakable shape of a predator.
Knut turns half on June 5 after six glorious months for Berlin Zoo which has hand-reared the celebrity polar bear from a guinea pig-sized baby into a powerful 28-kilo fighter. He'll be spending the day munching fish and playfully biting his faithful keeper Thomas Dörflein. It's a friendship that can last six more months at most.