The BBC's Malcolm Brabant looks at why student anger erupted across Greece over the fatal police shooting of a teenage boy.
Young people have been clashing with police in cities across Greece
The riots that swept Greece underline why the most important day in the national calendar is "Oxi" or "No" day.
"Oxi" day commemorates 28 October 1940, when Greek leader Ioannis Metaxas used that single word to reply to Mussolini's ultimatum to allow Italy to invade Greece, propelling his nation into World War II.
When Greeks say no, they mean it in spades.
Rebellion is deeply embedded in the Greek psyche. The students and school children who are now laying siege to police stations and trying to bring down the government are undergoing a rite of passage.
They may be the iPod generation, but they are the inheritors of a tradition that goes back centuries, when nuns would rather hurl themselves to death from mountain convents than submit to the ravages of Greece's Turkish Ottoman invaders.
'Springboards for violence'
The centre for this December rebellion is the Athens Polytechnic, where students have been out on the streets with wheelbarrows and shopping trolleys to collect and recycle rocks and pieces of marble used in the previous night's assaults.
The violence began in Athens and then spread to Thessaloniki
The polytechnic is the symbol of modern rebellion.
On 17 November 1973, tanks of the then six-year-old military dictatorship burst through the iron railings to suppress a student uprising against the colonels.
The exact casualty figure is still unknown to this day but it is believed that around 40 people were killed.
The sacrifice of the polytechnic was so significant that the post-junta architects of Greece's new constitution drafted the right of asylum, which bans the authorities from entering the grounds of schools and universities.
That is why places of learning are the springboards for the current wave of violence and it also explains why many of the riots are in university towns.
Students and pupils have effectively been given carte blanche to carry on protesting, because their professors have declared a three-day strike.
'Out of control'
Although many of today's protestors were not born when the polytechnic gates were crushed by the tanks, the lesson of the students' martyrdom is a key component of every Greek child's school democracy curriculum.
The latent Greek contempt for the police, which has now erupted so volcanically, has its roots in the dictatorship, when the police were regarded as the colonels' enforcers and traitors to the people.
The death of 15-year-old Alexandros Grigoropoulos at the hands of an experienced 37-year-old policeman has precipitated a wave of nationwide violence unseen since the dictatorship.
Whether it will lead to the fall of the unpopular conservative government of Prime Minister Kostas Karamanlis is unclear.
It is premature to see the troubles as Greece's reprise of the Paris uprising of 1968.
One of the wisest observations has come from Nikos Konstandaras, the managing editor of Kathimerini, one of Greece's more sober and respected newspapers.
In an editorial entitled "Anger's teen martyr", Mr Konstandaras wrote that Mr Grioropoulos' blood would be "used to bind together every disparate protest and complaint into a platform of righteous rage against all the ills of our society.
"It will quickly become a flag of convenience for anyone who has a grudge against the state, the government, the economic system, foreign powers, capitalism and so on."
"If Greece had already appeared difficult to govern, it will now be out of control."