Cannabis campaigners in Germany lit celebratory joints on Monday as new laws liberalising usage of the drug came into force.
Under the legislation, over-18s are allowed to possess substantial amounts of the weed for recreational purposes.
Individuals can grow up to three plants on their own.
The German Cannabis Association, which campaigned for the rules, staged a “smoke-in” at Berlin’s landmark Brandenburg Gate at midnight.
Other public consumption events were scheduled throughout the country, including one in front of the Cologne cathedral and others in Hamburg, Regensburg and Dortmund.
The change - on April Fool’s Day - was passed by Chancellor Olaf Scholz’s ruling three-party coalition in the Bundestag, Germany’s parliament.
Possessing up to 25 grams, equivalent to dozens of strong joints, is to be allowed in public spaces.
In private homes, the legal limit will be 50g.
Strict rules making marijuana difficult to buy paved the way for clubs where up to 500 smokers can gather from July 1.
Marcel Ritschel, a punter celebrating the new freedoms, told BBC News: “Some German people drink their beer after work.
“We just want to smoke our weed.”
But Alexander Poitz, of German police union Gewerkschaft der Polizei, issued a stark warning.
He believes chaos will follow instead of killing off the black market and protecting smokers from contaminated cannabis or organised crime gangs.
Mr Poitz said cannabis demand will quickly outstrip legal supply, given growing it at home requires perseverance and care, while it will be months before cannabis clubs can function.
Criminal networks will adapt and even “infiltrate” the social clubs while enforcing the law will be a “mammoth”, he claimed.
Already in some parts of Berlin, police often turn a blind eye to smoking in public, although possession of the drug for recreational use is illegal and can be prosecuted.
Some 4.5 million Germans are estimated to use cannabis.
Usage among 18 and 25-year-olds has doubled in the past 10 years, health minister Karl Lauterbach said.
Germany becomes the ninth country to legalise recreational use of the drug, which is also legal in some sub-national jurisdictions in the United States and Australia.
Many more countries allow its medical use as a painkiller.
Cannabis remains illegal for minors as does consuming it near schools and playgrounds.
