Airports are no place to sleep, as any weary traveler who has tried to grab a few minutes shuteye during a layover can attest.

But that may be changing, thanks to a new breed of short-stay, pay-by-the-hour micro-hotels popping up in airport terminals around the world.

Based loosely on the concept of the Japanese "capsule hotel," these cabins and boxes allow sleepy travelers to seal themselves off from the surrounding commotion for a 30-minute power nap or a solid night's sleep without having to leave the terminal for a hotel. Some even contain toilets and showers.

In recent years, versions of the concept have emerged from London to Moscow and from Philadelphia to Dubai, with other destinations likely to follow this year.

Diana Magnay looks at a novel idea to get 40 winks during a layover.

And they are spreading beyond the airport terminal. Yotel, which operates short-stay "cabins" in airports in London and Amsterdam, has also opened a hotel in Manhattan based on a similar concept, while Sleepbox, which has a demonstration model in Moscow's Sheremetyevo Airport, will open 60 of its units in downtown Moscow in a matter of weeks.

Here are three of the best micro-hotels proving that size isn't everything.

A Yotel premium cabin. Courtesy Yotel

Yotel has operated its pod hotels in London's Heathrow and Gatwick airports since 2007, and in Amsterdam's Schiphol since 2008.

Described by the company as being "inspired by first-class airline cabins," and by one user review as "a cross between a train compartment and a space ship," these small units pack in single or double beds, entertainment systems, a work desk and an en suite bathroom into between 7 to 10 square meters.

The cabins --32 at Heathrow, 46 at Gatwick and 57 at Schiphol -- cost about £25 ($39) for four hours, or about £60 ($93) overnight.

Yotel also operates a hotel based on a similar concept in New York City, with 669 slightly larger rooms.

Yotel marketing director Jo Berrington said the airport cabins had very high occupancy rates, and the company planned to roll out its operations in other airports soon.

Napcabs. Courtesy Napcab

Napcabs are 4-square-meter, self-service booths operating in Terminal two of Munich Airport. Six cabins are currently in operation, with plans to add more in coming months. They contain a bed, desk, air conditioning, internet access and a TV.

The minimum charge for their use is €30 ($38), which buys two hours between 6am and 10pm, or three hours outside those times. The company says it is moving to other airports shortly.

The cozy, 4-square-meter Sleepbox contains a maximum of three bunk beds, bedside tables, electrical outlets, and reading lamps and can be equipped with a television and alarm clock. A model Sleepbox was installed in the Aeroexpress terminal of Moscow's Sheremetyevo Airport in August, and will be put into commercial use in coming weeks when 60 are installed for use in downtown Moscow.

The Sleepbox's designers envisage the units will also be used in train stations, shopping malls and exhibition centers. They can be booked for as little as 30 minutes; Sleepbox recommends a usage charge of U.S. $15 an hour.

Minute Suites Minute Suites

Minute Suites provides private rest spaces for travelers to relax, nap or work inside the security areas at two U.S. airports.

Atlanta's Hartsfield-Jackson International Airport has hosted the micro-rooms since late 2009. Philadelphia International Airport also installed 13 suites in 2011.

Standard features include a daybed sofa and an HD television. A desk, phone, office chair and Wi-Fi internet connection ensures each suite can also act as a makeshift office space.

A minimum one-hour stay costs $30, while every 15 minutes thereafter is charged at a rate of $7.50.

Situated in Terminal one of Dubai International Airport, SnoozeCube offers a compact and soundproof room complete with bed, touchscreen TV and internet access.