Duncan Bartlett discovers how, when it comes to lavatories, Japan is a step ahead of the rest of the world.
No country takes toilets quite so seriously as Japan.
Machines with heated seats, built-in bidets and a dynamic range of flushing options are almost ubiquitous in homes and public buildings.
A poem recently published by a stressed-out salary man captured their comforting appeal with haiku-like brevity. "The only warmth in my life is the toilet seat," he mourned.
But lavatories here can do much more than keep you warm. One even sends a tiny electrical charge through the user's buttocks to check their body-fat ratio.
The master of the modern convenience is the Panasonic Corporation.
At its Tokyo showroom, located in a skyscraper near the BBC's office, a group of smart young women, dressed in uniforms resembling flight attendants, showed me the company's latest wares.
The lids lifted up when I approached. If I stood in front of one, it took a guess at my gender and lifted up the seat as well.
There was a loo that glowed in the dark and another that had built-in loudspeakers.
With manicured fingernails, the demonstrator pushed the control panel beside the seat and gentle light classical music began to play.
Pleasant enough, I thought, although I preferred a pastoral sound effect that provided the impression one was seated upon a white plastic throne surrounded by songbirds in a springtime meadow.
Kyoko Ishii, who heads up the public relations department for Panasonic, explained to me that most of the people who choose luxury loos are older women, so this is a booming market in rapidly ageing Japan.
Kyoko says that for this core customer group, the emphasis now is less on the gadgetry and more on convenience and cleanliness.
A new flush has been invented which does away with the need for a tank and saves dramatically on water.
The device costs about £1,950 ($3,000) including installation. But it is not easy to sell outside Japan as bathrooms in other countries are rarely fitted with the right mixture of sophisticated plumbing and electronics.
A visitor to Tokyo recently told me that he was surprised to find Japanese women rather than foreigners cleaning the toilets in his hotel.
It is of course often immigrants who take on such jobs in rich countries. But foreign-born workers are rare here as only about 1.5% of the population are made up of non-native Japanese.
However, the low immigration level is only part of the explanation. Japanese people do not see cleaning as a demeaning or shameful job.
School children are trained from a young age to sweep their classrooms and scour the playground for litter.
Lorry drivers wash their trucks at the end of every day. No restaurant ever serves a meal without first offering the customer a cleansing towel.
Recently, I visited a small technology company in Osaka. The president, Mr Sugimoto, is trying to inspire his staff to work harder as recession takes hold.
He is noted for his drive and enthusiasm and that came across in a punchy presentation which he showed me on his laptop.
It included photographs of his staff on their knees scrubbing the urinals.
His point was that in preparation for a new project, the whole team had mucked in to clean up the workplace and this was clearly a source of pride to be included in the company's publicity.
Source of comfort
But toilets can raise a smile, too. Television comedies sometimes include scenes of pranksters luring people into loos whose walls then collapse, and the embarrassment this causes the victim is a source of great hilarity.
The Japanese - like the British - do not seem to mind too much when comedians sink into vulgarity and joke about scatological matters.
But there is also a dark underground trade in DVDs filmed in ladies' toilets by hidden cameras, and only last week a man was arrested for placing "spycams" in the lavatories of a girls' school.
Most of the time, though, the Japanese are happy to think of a toilet as their comfort and their friend.
The other day, while catching a commuter train to work, I found myself transfixed by an advertisement which was being screened on a TV inside the carriage.
A young girl slowly walked towards a loo, which automatically raised its lid to greet her.
The toilet then appeared to give a welcoming robotic smile and its seat began to glow an inviting orange colour as it heated up, ready for action.
Fortunately, the advertisement ended there. But not before a broad and appreciative smile broke out across the face of the girl.