The Irish Republic has become the first country in Europe to pass laws banning branded cigarette packets.
Following the example set by Australia, all tobacco products will be sold in a standard dark-coloured wrapper emblazoned with large health warnings and images of disease.
Slim boxes of cigarettes, in lipstick-style shapes, will also be illegal under the reform.
Brand names will be small and use similar fonts on all packets in the marketing clampdown which is likely to be challenged in the courts, either in Ireland or under European rules.
The UK is set to follow the Irish example with laws to be passed before the end of the month.
James Reilly, Irish children's minister and a former health minister who spearheaded the ban, said it was about protecting people and should be seen as a good day for the health of children.
"Standardised packaging will strip away the illusions created by shiny, colourful cigarette packets and replace them with shocking images showing the real consequences of smoking," he said.
Up to 10 European countries are understood to have complained over the Irish branding ban.