Here's a look at what happens after the plants are taken offline.

- Gradual shutdown -

On the day of the shutdown, plant operators will gradually decrease electricity output.

From 10:00 pm (2000 GMT), "we will lower the facility's power output by 10 megawatts per minute", Carsten Mueller, plant manager for the Isar 2 site near Munich, told the Bild newspaper.

When the reactor's power level drops to around 30 percent, "no more electricity will be fed into the high-voltage network and the generator will be automatically disconnected from the power grid", he said.

A similar process will take place in the turbines of the Emsland plant in northwest Germany and at Neckarwestheim in the southwest.

The Neckarwestheim plant has already been running "at about 70-percent capacity" since mid-January, said Joerg Michels, head of the nuclear power division at energy company EnBW, which operates the site.

Bringing a nuclear plant to a halt is actually a "routine process" often used during inspections, Michels said.

"What's unusual now is that it will happen for the last time."

Once the nuclear reactor is rendered less powerful, it will no longer send hot, pressurised water to the machine room, where the turbines will subsequently stop producing electricity.

Although no ceremonies are planned at Neckarwestheim to mark the occasion, management will be on site "out of respect" for the roughly 650 remaining employees, Michels said.

- Cooling and dismantling -

Over the following days, the atomic chain reaction sustained by the nuclear fuel rods will be "completely stopped" to allow for the "cooling of the plant's nuclear cycle", Michels said.

As part of its exit from nuclear energy, Germany has opted for the immediate dismantling of the plants once they have been disconnected from the grid, rather than mothballing the facilities.

At Neckarwestheim, the 193 fuel elements in the reactor's core -- which are still highly radioactive -- will be transferred to a water-filled pool in an adjacent building.

The fuel elements will remain immersed for three to five years until they are packed into special "Castor" casks for interim storage.

The dismantling of each component of the power plant will start "at the beginning of next year", once all the permits have been obtained, Michels said.

"We are well prepared," he added, given that EnBW already has four other reactors undergoing dismantling.

The dismantling of Germany's last three nuclear installations is expected to take around 15 years.

- Final resting place -

Germany plans to bury its highly radioactive waste deep in the ground.

But the decision on where exactly this last resting place should be is taking longer than planned, with suggested locations often running into opposition from nearby residents who fear health hazards.

A choice on the final repository was initially due by 2031, with the aim of having the site operational by 2050.

But late last year the German body in charge of nuclear waste disposal said a suitable location would likely be found only between 2046 and 2068.

Once the site has been identified, the planning, licensing and construction of the repository is expected to take around two decades.

The final repository eventually selected must be able to safely store radioactive waste for a million years.

In the meantime, the highly radioactive waste will be held in specially designed interim storage facilities.

For medium- and low-level radioactive waste, a permanent repository has already been found at the former Konrad iron ore mine near Salzgitter in central Germany. The site is set to become operational in 2027.

"More than 30,000 generations will still be affected by the consequences of nuclear power technology, which has only been used in our country for 60 years," former environment minister Barbara Hendricks said in 2017.