Most members of the Thai youth football team rescued from a flooded cave have had their heads shaved as part of a Buddhist ceremony to ordain them as novices.
Their coach is also receiving monk's orders. One of the boys is not joining the ceremony as he is a Christian.
The group will spend nine days living in a monastery, a tradition for males in Thailand who experience adversity.
They were trapped for more than two weeks before a dramatic rescue.
The boys were all released from hospital last week and are said to be in good health after their ordeal in the snaking caverns of the Tham Luang caves of northern Thailand.
This step is intended to be a "spiritual cleansing" for the group, and to fulfil a promise by the families to remember one of the divers who died in the rescue operation.
"They should spend time in a monastery. It's for their protection," Seewad Sompiangjai, grandfather of Night, one of the rescued boys told the BBC earlier. "It's like they died but now have been reborn."
They will stay in different monasteries until 4 August meditating, praying and cleaning their temple. The length of time they will spend doing this - nine days - is a nod to a Thai lucky number.
Correspondents say it's seen as normal by Thais for boys and men to spend time as monks as a rite of passage.
One of the boys, Adul Sam-on, will not be joining the rest of the "Wild Boars" football team as he is a Christian. Their coach Ekkapol "Ake" Chantawong, 25, will join them for the same period of time but as a fully fledged monk rather than a novice.
The coach had spent time in a monastery as a novice before this. Although he has attracted some criticism for taking the boys into the cave, he is also credited with helping them through the ordeal by reportedly teaching them meditation techniques to help them stay calm and use as little air as possible.
A risky operation
The extraordinary story of the group's rescue has been followed by millions worldwide since 23 June, when they walked into the Tham Luang cave after football practice - only to be trapped by sudden monsoon floods.
The 12 boys and their football coach had spent nine days in the cave with little food or light when British divers helping search for them first reached them on 2 July.
But with more rain expected, a risky rescue was attempted. Expert divers guided the boys and their coach through darkness and submerged passageways towards the exit.
Each boy was accompanied by a diver who also carried his air supply. The boys were heavily sedated ahead of the rescue to prevent them panicking.
The boys and their coach were rescued in three stages over three days.
All 13 were transferred to a hospital in Chiang Rai where they received medical and psychological assistance.
Hundreds of volunteers, rescue divers and military personnel were involved in the rescue effort.
One ex-Thai navy seal diver, Saman Gunan, died during the operation while installing oxygen tanks in the cave.
The cave system has now been closed off, but officials have said it could be reopened in future as a tourist attraction.