Iran's youth are no strangers to operating underground.
They have spent years circumventing the Islamic Republic's strict religious laws that ban drinking and restrict freedom to sing and dance.
The laws, introduced after the 1979 revolution, mean that anything deemed "un-Islamic" or labelled by the regime as "causing corruption on Earth" or "propaganda against the government" could result in imprisonment, or in some cases, death.
Despite the risks Iranians face, there's a thriving underground music scene, with hip hop, rap and EDM dance parties.
Now the younger generation are using their underground networks to mobilise and coordinate public protests, in the hope they can topple the Islamic Republic.
Protests sparked in September by 22-year-old Mahsa Amini's death in custody have continued into the fourth month, despite a brutal crackdown by the regime that has so far resulted in 19,000 arrests and more than 500 deaths.
According to reports from Persian-language media outlets operating outside Iran, there's now an alliance of 30 youth groups inside the country, called the Neighbourhood Youth Alliance of Iran.
The group's members remain anonymous, but they use Twitter and Telegram to distribute manifestos calling for regime change.
Their stated goal is to overthrow the regime, and create an "inclusive, democratic government", which upholds fundamental human rights and is based around the separation of religion and state.
A regime under pressure and a movement seeking a secular state
Cameron Khansarinia, policy director at the Washington-based National Union for Democracy in Iran (NUFDI), says while the Islamic Republic apparatus remains intact, there have been some early signs of regime defection.
"You see reports of members of the armed forces refusing to clamp down on protesters — and as you see more of that, I think you'll begin to understand why people are beginning to call it a revolution," he says.
There have been other telling signs the regime's power is diminishing, with a growing number of sanctions from various countries including Australia.
The UK is expected to officially designate Iran's Islamic Revolutionary Guard Corps as a terrorist organisation, following several alleged plots to kidnap or murder UK citizens, and an Australian Senate inquiry looking into recent violence in Iran is being called on to do the same.
After months of campaigning by human rights activists in the diaspora, Iran was expelled from the UN Commission on the Status of Women in December, and the UN Human Rights Council has appointed a review into Iran's rights violations.
It's unclear who inside Iran would lead new government, but what is evident is that Iranians are no longer willing to support the idea that the Islamic Republic can be reformed.
With the protests spreading to more than 160 cities in 31 provinces, people of all cultures and classes are now openly chanting, "down with the dictator".
The chants may have started with women protesting against the forced hijab, but it quickly shifted — now merchants, truck drivers and oil refinery workers are among those striking and calling for an end to the Islamic Republic.
According to recent surveys by the Group for Analyzing and Measuring Attitudes in Iran (GAMAAN), 74 per cent of women and 71 per cent of men in Iran disagree with laws imposing hijab on women.
Of those opposed to compulsory hijab, 84 per cent want to live in a secular state.
GAMAAN's polls, which surveyed tens of thousands of Iranians inside the country in mid-2020 and early 2022, linked this to a decline in religiosity, with the "overwhelming majority" of Iranians no longer praying five times a day or saying they believe in wearing the hijab.
This includes older Iranians — 59 per cent of those aged over 50 do not observe prescribed prayers and 55 per cent do not agree with wearing hijab.
The surveys also showed secularisation increasing in rural and urban Iran.
And the movement also has the support – both publicly and quietly — of the millions of Iranians that left Iran after the 1979 revolution but remain active in the diaspora.
Ensuring the revolution 'is not hijacked like it was in 1979'
Shahin Milani, a legal analyst and executive director at the Iran Human Rights Documentation Center (IHRDC), says the major tipping point came when Iranians boycotted the 2021 elections.
He says for many years Iranians thought the elections were a choice of the lesser of two evils – the so-called reformists amongst the regime, versus the hardliners.
"I think that now the trajectory is clear — the Iranian people really don't want this regime anymore," he says.
If the Iranians do succeed in regime change, there are fears that individuals or organisations that are not representative of the people's goals and desires could step in to take over the revolution.
Iranian-Australian barrister Faraz Maghami says this is effectively what happened in 1979, when Ayatollah Khomeini appointed himself as supreme leader after the fall of the Shah.
Maghami says that the "hijacking of the 1979 revolution" happened because there was no structure.
"There were a lot of political commentators, a lot of political activists, a number of different groups, who came together very loosely, with one intent, which was to overthrow the Shah," he says.
"But what not a single one of them had executed properly was a plan for transition."
He says this time around, Iranians must avoid a repeat of the revolutionary courts in 1979 that saw Ayatollah Khomeini "appointed as the chief judge, jury and executioner".
"We need to make sure this movement is not hijacked," he says.
Behnam Ben Taleblu, senior fellow with the Foundation for Defense of Democracies (FDD), says that Khomeini's platform only grew when he was exiled.
"There is a connective tissue, between the diaspora community, and the dissident community and the population in Iran," he says.
"These different iterations of nationalist protests from 2017 have been building those bonds, perhaps not as quickly as we might like to have them grow. But they are they are growing."
Maghami believes if Iranians topple the regime and elect new leaders, diaspora groups like the coalition of Iranian lawyers that he is part of will assist as legal guardians of the process, helping to draft a new constitution based and the needs and wants of the people.
A call for leadership, not one leader
Abbas Milani, director of Iranian studies at Stanford University, says no-one in Iran is expecting one leader to step forward, even though that has been the case in previous revolutions.
"People feel betrayed by that charismatic leader, Khomeini, who promised a democratic republic and delivered despotic clerical regime," he says.
"It convinced people to no longer seek one charismatic leader. They're trying to seek leadership, which is different."
Instead, he says Iran's youth have created "defacto networks of organisations" and leadership committees to help with the transition, and various business leaders, actors, athletes, media personalities, academics, lawyers and doctors have come forward to help.
Milani says the leaders will come from inside Iran, but they can only emerge when the regime falls and there are free and fair elections.
"I've been in the diaspora for 35 years … I have never, ever seen the Iranian community at large, whether inside or outside Iran, as dedicated as organised as mobilised in trying," he says.
Some prominent names in the diaspora that have been put forward as those who could assist in that transition include the former crown prince of Iran Reza Pahlavi, activists Hamed Esmaeilion, Nazanin Boniadi and Masih Alinejad, environmentalist Kaveh Madani, and soccer player Ali Karimi.
It's unclear how much support these individuals have inside Iran, but NUFDI's Cameron Khansarinia says he would classify many of them as among a "secular democratic mainstream opposition".
"For a long time, there was this misconception — propaganda pushed by the Islamic Republic itself — that those in exile are extremely disconnected from the realities on the ground," he says.
"But actually, the Iranian diaspora, particularly the Iranians exiled — those that were forced to leave the country — are extremely well plugged-in to events in their home country."
While it would be difficult for the movement to be successful without leadership from both outside and inside the country, Khansarinia says Iranians are not asking for the West to "do regime change for them".
"They are very capable and very indeed willing to bear a significant brunt of the risk, of the cost, for change in their country, themselves," he says.
But the diaspora will back them.
What happens if the protesters fail?
For many activists outside Iran, who have been lobbying their governments and supporting those inside Iran in other ways, the possibility that the protest movement might fail is too hard to accept.
"I don't like to think about this, but if the movement were to fail, and Khamenei and his regime remains, then the response from them would likely be terrifying," geopolitical risk expert Pyotr Kurzin says.
"If attempted resistance movements in other places are anything to go by, such as Myanmar since 2021 after a coup overthrew the government, there would be mass suppression — think nationwide enforced curfews and removal of any online access.
"They'd likely try identifying and targeting the people they deemed to be the biggest drivers of the protests, both inside and out of Iran, and l wouldn't be surprised if parts of the diaspora's safety became compromised."
Kurzin says the widespread nature of strikes across the country indicate that "people are more driven by the cause to overthrow the regime, than they are to earn an income and support themselves".
His fear is that the protests could fizzle out "if people get too intimidated by the executions, or if the Iranian military chooses to get more involved".
"Revolutions are marathons, not sprints – they take sustained, committed and coordinated work to ensure they succeed to the end," he says.
Iranian-American activist Mariam Memarsadeghi is determined not to imagine failure. Instead, she says, "we are at a place of no turning back".
"We need to think about how horrific defeat would be — just as if Putin manages to win in Ukraine — the level of violence and brutality that we see today is going to be nothing like what will come after it," she says.
Alireza Nader, an expert on Iran and US policy in the Middle East, says to ensure the protest movement doesn't fail, world leaders could close Iranian embassies around the world and curtail trade with the regime by killing the nuclear negotiations.
"Either you support freedom for the people of Iran or your support a deal that gives the regime tens of billions of dollars," Nader says.
Abbas Milani says the regime wants Iranian people to fear the government's violent crackdowns and give up protesting.
"They might well succeed in slowing down this movement, but I am convinced that they're not going to be able to solve their problem by brutalising their way out of this," he says.
Iran's leaders, he argues, are made up of "septuagenarian reactionary men, ruling over 21st century society, with ideology that is 1400 years old".
"The assumption that you can compromise your way with this regime, if you make concessions to this regime, and the regime will then change this behaviour is fool's gold," he says.
"This regime thinks dancing is a sign of devil. It thinks joy is trickery of the devil, it thinks women are complicit with the devil. It can't last."
And with mounting economic problems after years of high inflation, high unemployment and a tumbling currency, all of which Milani says the regime has failed to solve, things will soon come to a head.
"This is a seething volcano," Milani says.
"There might be a brief interruption, but the volcano will erupt."