A new law making it illegal to smoke in a car with anyone under the age of 18 has come into force in Scotland.
Legislation aimed at protecting children from second-hand smoke was unanimously passed at Holyrood in 2015.
Smokers' rights campaigners have dismissed the change as pointless "virtue signalling".
Public Health Minister Aileen Campbell said the "poisonous chemicals in second-hand smoke" were particularly dangerous to children.
People caught breaking the new law could face a fine of up to £1,000.
But Ms Campbell said the point of the law was to change behaviour rather than punish people.
Speaking on BBC Radio's Good Morning Scotland programme, she said: "Six months from now, from the point when the legislation goes live today, we are seeking there to be no on-the-spot fines so there is a concentration on awareness raising and education across the country."
The law came about via a members' bill by then Lib Dem MSP Jim Hume in the previous session of parliament, and came into force at midnight.
Mr Hume, whose mother died of cancer caused by second-hand smoke, introduced the Smoking Prohibition (Children in Motor Vehicles) Bill and won unanimous backing from MSPs.
A similar law came into force in England and Wales in 2015, although there have been difficulties over enforcing the ban.
Research shows that second-hand smoke can cause serious conditions including bronchitis, pneumonia and asthma.
Ms Campbell said: "It's simply not safe to smoke when a child is in the car. Dangerous levels of chemicals can build up, even on short journeys, and 85% of second-hand smoke is invisible and odourless so you can't always see what they're breathing in.
"We know for a fact that the poisonous chemicals in second-hand smoke are extremely damaging to our health. We also know that children breathe faster than adults, meaning they ingest more of the deadly toxins."
Mr Hume added: "It fills me with great pride that through hard work and cross-party consensus we are now seeing the introduction of a law which can potentially save 60,000 children a year from the hazards of second-hand smoke.
"I thank all members of the previous Parliament's health and sport committee for their constructive work, the ministerial team, fellow members, the numerous charities, organisations, academics and my own office who have supported me.
"There is one other person I would like to thank; a woman who inspired me and drove me on to make a difference in my community, a non-smoker who died five years and one week ago today from lung cancer, my mother, Joyce Hume.
"Thanks to all those in support of this measure, we have taken a huge step in the right direction to having a healthier Scotland for all."
The move has won backing from health and anti-smoking groups.
'Tobacco free generation'
Sheila Duffy, chief executive of health charity Ash Scotland, said: "We know from speaking to parents that they want to protect their children from tobacco smoke, but often don't know enough about how smoke is harmful and lingers in the air even after you can't see or smell it.
"This legislation sends a clear message that children should grow up in a smoke-free environment, and who could disagree with that?"
Irene Johnstone, head of the British Lung Foundation in Scotland, added: "This new law will not only help reduce the exposure of second hand smoke, but will also go a long way in helping Scotland becoming a tobacco free generation."
However the smokers' group Forest has criticised the new law as "utterly pointless".
Its director Simon Clark said: "The regulations are patronising and unnecessary. Very few adults smoke in cars with children. Smokers know it's inconsiderate and the overwhelming majority don't do it.
"So few people smoke when there's a child in the car it will be like looking for a needle in a haystack. In England only one person has been caught and fined since an identical law was introduced last year.
"The law is a classic example of virtue signalling. It's utterly pointless and a complete waste of time and resources that could be better spent elsewhere."