Prince George and Princess Charlotte were greeted by rain when they arrived in Poland with the Duke and Duchess of Cambridge for the start of their parent's European tour.
The royal children flew in a private chartered plane with William and Kate, and the couple's entourage, before touching down at Warsaw Chopin Airport.
Despite the light downpour, Charlotte was carried by her mother down the plane's steps while George held his father's hand as he slowly walked down.
The royal children were smartly dressed, with the future king in a shirt and shorts and his sister wearing a summer dress.
At the bottom of the steps waiting to greet them was Jonathan Knott, Britain's ambassador to Poland, his wife Angela, and the diplomat's Polish counterpart in Britain Arkady Rzegocki.
Charlotte, two, and three-year-old George were last seen in public on Buckingham Palace's balcony watching the flypast following the Trooping the Colour ceremony.
The trip, which will also take them to Germany, is another milestone in their royal lives as it is the first time they have been on an official tour of Europe.
William and Kate have taken their children on tour before, travelling to Canada with them last year where they enjoyed an open-air party for youngsters.
And in 2014 the young prince flew with them to New Zealand and Australia for their extensive visit.
But during the tour of Poland and Germany the children will only be seen during arrivals and departures in the two countries and possibly one other event.
With George starting school in south London this September, attending the mixed-sex Thomas's Battersea school, and his sister likely to be enrolled in a nursery, this is the last time the royal couple will be able to take their children with them without school commitments making it problematic.
William and Kate's trip, taken at the request of the Foreign and Commonwealth Office, is likely to be seen as another Brexit diplomacy tour, helping to maintain and strengthen the UK's relations with Europe as it leaves the EU.
Charlotte clung on to her mother's neck as Kate was introduced to the small entourage at the base of the plane's steps, while William was ahead of her holding on to his son's hand.
George fidgeted, swinging his right leg backwards and forwards before wrapping it around his left as William smiled and shook hands as the royal couple's five-day visit began.
The foursome ignored the light rain and walked along a red carpet into a small terminal past the large group of media and on to a meeting with Poland's President Andrzej Duda.
Kate wore a white Alexander McQueen outfit, and her new haircut dubbed the "Kob", Kate bob, which was debuted during a visit to Wimbledon last week, appeared unaffected by the rain.