A landmark new law on organ donors comes into effect in Wales today.
The revolutionary system means adults automatically become donors after their death - unless they have chosen to opt out beforehand.
Some religious groups have criticised the move, but health officials argue that it will save hundreds of lives.
The Welsh Government predicts the new law could increase the number of organ donors by as much as a quarter.
Wales' health minister Mark Drakeford said: "The latest figures show 14 people died last year in Wales while waiting for a transplant.
"The change to a soft opt-out system for organ donation will deliver a revolution in consent.
"Organ donation saves lives; increasing the rate of organ donation allows us to save more lives. That's the key motivation for this significant change."
Under the new system, those over 18 will become potential donors either by registering their decision to opt in - as they do currently - or by doing nothing at all.
It will apply to adults who have lived in the country for more than 12 months.
Organs available will be the same as the "opt-in" method - including kidneys, heart, liver, lungs and pancreas - and would go anywhere in the UK.
According to the latest figures, 1,000 people in the UK die every year while waiting for a transplant.
In Wales, there are currently 224 people on the waiting list for an organ transplant, including eight children.
Among those welcoming the new law in Wales is the British Heart Foundation (BHF) which says the rest of the country should follow suit.
BHF chief executive Simon Gillespie said organ donation rates in the UK are 40% lower compared with other countries in Europe that already use the opt-out system such as Spain and Croatia.
"Sadly hundreds of people die every year waiting for a transplant because there is a desperate shortage of organ donors," he added.
"Other European countries that already use an opt-out system have much higher donor rates than the UK.
"We campaigned strongly in Wales to introduce soft opt-out and now it's time for the rest of the UK to follow their lead."
The change has also prompted praise from those on the transplant list too.
Jon Williams, 43, of Wrexham, has end stage heart failure and is one of only 60 people in the UK being kept alive by a Left Ventricular Assisted Device (LVAD).
Mr Williams, who has been on the waiting list for two-and-a-half-years, added: "I'm very lucky the LVAD has given me some quality of life back but I am aware that my condition will deteriorate further at some point so it is only a matter of time until I need a new heart.
"In the meantime it's important to stay positive and hopefully when my condition becomes critical a suitable donor heart will become available."
Ahead of the new law coming into effect, several faith groups - featuring signatures of leading Welsh Christian, Jewish and Muslim clerics - signed an open letter expressing their unease about the plan.
It said: "We remain opposed to any weakening of the principle the donation of organs should be free and voluntary."
And The Archbishop of Wales, Dr Barry Morgan, previously expressed fears that the scheme could turn "volunteers into conscripts".
But in an open letter published today, Church of Wales bishops called on people to make a positive decision one way or the other.
It said: "As Bishops we are wholeheartedly in favour of organ donation.
"It is love in action and a wonderful example of what it can mean to love our neighbours, especially those in need. Such generosity is a response to God's generosity towards us.
"We urge and encourage you to sign the Organ Donor Register, and tell your families, so that there can be no doubt about your wishes in the event of your death."
According to the latest figures, only 8% of eligible adults in Wales have decided to opt out ahead of the new law today.