The earthquake in March 2011 was the most serious disaster in Japan's history. At least 3,000 people died, and more than 15,000 people are still missing.
Around 500,000 people have been evacuated, and are sleeping in temporary shelters. The north-eastern areas of Miyagi, Iwate and Fukushima are worst affected.
Many towns were completely flattened by the quake and tsunami. In total more than 76,000 buildings have been damaged and at least 6,300 were completely destroyed.
An enormous rescue effort has been launched. So far 102 countries have sent help to Japan, including food, medicine and search dogs.
Even miles from the epicentre, normal life has been disrupted. Food and fuel supplies are running low as far away as Tokyo.
Electricity has been switched off in some areas to save power. A quarter of Japan's electricity comes from nuclear power and the quake has closed 11 nuclear reactors.
One of the big problems is that is is freezing cold, and there is limited electricity, in some of the worst affected areas.
Charities think it could take years for everything to get back to normal. Buildings have been flattened and roads reduced to rubble.