As union leaders and employers return to the negotiating table Thursday, here's what you need to know about IG Metall's groundbreaking campaign to rethink the work-life balance - and what it could mean for the rest of the country.
What do they want?
IG Metall represents some 3.9 million workers in Germany's crucial metal and electrical engineering industries.
As in past industry-wide negotiations with employers, it is pushing for a wage hike - this time seeking a whopping six-percent increase.
But most striking in the current showdown has an emphasis on giving employees the freedom to tailor their work hours to their personal lives.
The union wants all workers to have the option of switching from a 35- to a 28-hour week for a two-year period, with a guaranteed return to full-time work afterwards.
In certain cases - and this has been the most headline-grabbing demand - the union says employers should make up some of the salary loss that would result from clocking up fewer hours.
It wants those caring for young children or elderly relatives, for example, to receive an extra €200 a month.
And shift workers or others whose working hours can weigh on health should be entitled to an additional €750 annually, it says.
What are the arguments for a shorter week?
IG Metall says flexible working time has so far mainly benefited employers who got staff to put in longer days.
But with Europe's top economy humming and unemployment at a record-low, it believes the time is right for a radical shake-up.
"Workers aren't only workers, they have personal lives, children, old parents," Berlin IG Metall chief Olivier Hoebel told strikers at a demonstration on Monday. "Working life can't only be about sacrifice."
IG Metall believes its proposals would especially benefit women, large numbers of whom work part-time for family reasons and currently don't have an automatic way back to full-time employment when their situation changes.
How have employers reacted?
With a firm 'no'.
The Gesamtmetall employers' federation has predictably balked at the suggestion of paying staff extra to work less.
It has dismissed the proposals as "too costly" and "unfair" to those already in part-time work under less generous conditions.
It says introducing the compensation measure would be discriminatory and open companies up to legal action.
After two rounds of negotiations, employers have so far offered a two-percent wage increase, but no progress has been made on the 28-hour issue.
What would the impact be?
Where IG Metall goes, others tend to follow.
Europe's largest trade union was instrumental in pushing through a 35-hour working week in the 1990s, and employers across Germany are closely watching to see if the next labour revolution is around the corner.
Already the call for a shorter week has triggered heated debate about quality of life and the future of work in a world where jobs are increasingly automated.
Supporters have praised the union's proposals as "very modern" and said they could help firms hang on to their best and brightest.
But critics have countered that a reduced week could exacerbate a shortage of skilled workers, while smaller firms in particular might struggle to meet production targets.
"If it would be replicated throughout the economy, it could do serious damage," said Holger Schmieding, chief economist at Berenberg bank .
Gesamtmetall estimates that some 1.5 million workers would be eligible for the proposed compensation if they chose the 28-hour route. IG Metall however believes the actual take-up would be far lower.
Where to go from here?
A third round of talks starts Thursday, but there's little hope of a breakthrough.
IG Metall raised the stakes this week, with tens of thousands of workers launching hours-long "warning strikes" at dozens of firms including Volkswagen, BMW and Siemens.
It has vowed to call day-long walkouts if the standoff continues and even threatened to stage the union's first nationwide, open-ended strike since 2003.
"If on Thursday we still can't see a willingness to seriously talk about these issues, the situation will escalate," IG Metall chief for southwestern Germany, Roman Zitzelsberger, told the Handelsblatt financial daily.