London (CNN) -- Prince George made his first public appearance in three months Wednesday, as he arrived with his parents, Prince William and Catherine, Duchess of Cambridge, for his christening at St. James's Palace.
The baby prince smiled as he was shown off to family members including his great-grandparents, Queen Elizabeth II and Prince Philip, before the royals entered the Chapel Royal.
George was dressed in an elaborate lace and satin christening gown that's a replica of one made in 1841 for the christening of Queen Victoria's eldest daughter.
Being baptized into the church is more significant for George than for most people, since he is in line to become king, which would also make him the supreme governor of the Church of England.
The occasion has been kept uncharacteristically small, in a shift away from the larger ceremonies that his father and grandfather enjoyed at Buckingham Palace.
His grandfather Prince Charles and uncle, Prince Harry, are among the select few invited to the ceremony, along with Catherine's parents, Carole and Michael Middleton, and her siblings, James and Pippa.
The Archbishop of Canterbury, the Most Rev. Justin Welby, greeted the guests as they arrived at the chapel.
The royal baby, who was born in July, will have seven godparents, among them Prince William's cousin Zara Tindall, daughter of Princess Anne, and close friends of the couple.
They include Oliver Baker, who got to know William and Catherine at St. Andrew's University, Emilia Jardine-Paterson, who went to school with Catherine, and William van Cutsem, a childhood friend of William.
The other godparents are Jamie Lowther-Pinkerton, a former private secretary to the Duke and Duchess of Cambridge and Prince Harry; Julia Samuel, who was a good friend of William's mother, Diana, Princess of Wales; and Earl Grosvenor, son of the Duke of Westminster.
The replica christening gown was brought into use in 2008 to help preserve the 170-year-old original, used until then for every royal christening, including those of Prince William and his father, Charles.
The venue for the christening also has a special significance for Prince William. The body of his mother, Diana, rested in the Chapel Royal for five days before her funeral in 1997.
After the service, Prince Charles and Camilla, Duchess of Cornwall, will give a private tea at Clarence House. The guests will be served slices of christening cake, which is a tier taken from William and Catherine's 2011 wedding cake.
'What a gift'
In a short video posted on his website, Welby spoke of the significance of the baby prince's baptism, which will see him "join the family of the church," numbering almost 2 billion people around the world.
Welby said any christening was a moment for the parents to celebrate the birth of their child, royal or not.
"All babies are unbelievably special, not only royal babies," he said.
But Prince George's christening does carry an extra significance, he said.
"As a nation we are celebrating the birth of someone who in due course will be the head of state. That's extraordinary. It gives you this sense of forward looking, of the forwardness of history as well as the backwardness of history, and what a gift to have this new life and to look forward."
As with any other infant's baptism, Welby will mark the prince with the sign of the cross on his forehead and splash water on his head.
The silver font to be used for George's baptism has been used for every royal christening since 1841 and will be filled with water from the River Jordan.
The 3-month-old boy has already made history. He's the first royal baby to be honored with a christening coin from the Royal Mint.
The design of the coins, produced by the Royal Mint in a range of sizes and materials, has been approved by his parents and the Queen, the Royal Mint said.
The public can buy the keepsakes, which start at 13 pounds ($21) for the simplest type but rise to a whopping 50,000 pounds ($80,000) for a version containing a kilogram of gold.