Small spaces are the next big thing in real estate.

Thanks to problems like rising housing costs, overpopulation, and environmental damage, it seems the solution is to think smaller. Much smaller.

Here are 20 of the smallest homes we could find around the world. They're on roofs, on wheels, and in backyards; they have bedrooms, bathrooms, and kitchens.

But just because they're small doesn't mean that they can't be livable--or beautiful, for that matter. Architects and designers have taken to the tiny home movement, creating beautiful designs that make the tiny spaces as efficient and livable as possible.

A Brooklyn couple bought smaller furniture to make their 350 square-foot apartment feel more spacious.

Image credit: Apartment Therapy

Size: 350 sq. ft.

Location: Brooklyn, New York

Homeowners Tiffany and Allan use small furniture instead of full-size pieces to make the most of their 350 square-foot studio in Brooklyn. The space was formerly the parlor of a ship captain's home from the 1800s, and still features the original crown molding and large, light-bearing windows.

Their home was the U.S. overall winner of Apartment Therapy's 2014 Small Cool contest.

This 330 square-foot apartment in Hong Kong transforms into 24 different room combinations.

Image credit: REUTERS/Bobby Yip

Size: 330 sq. ft.

Location: Hong Kong

Gary Chang, an architect in Hong Kong, turned his family's tiny 330 square-foot tenement apartment into a sleek and efficient living space with 24 different room combinations, including bathrooms, kitchens, living rooms, and even a guest bedroom area.

So, how does he do it? Chang installed a number of sliding panels which he can move around the space to reveal hidden areas and storage. It's a system he calls the "Domestic Transformer."

This 258 square-foot home in Barcelona was once an old pigeon loft.

Image credit: kirstendirksen via YouTube

Size: 258 sq. ft.

Location: Barcelona, Spain

When photographer Christian Schallert moved to Barcelona in 2003, he went searching for the perfect, affordable home. He found it in an old pigeon loft on top of a building, about 100 steps up.

When Schallert arrived, the 258 square-foot space was dirty and had not been maintained, but he designed and remodeled it into a warm, open, "Lego-style" apartment. The walls slide to reveal different room set ups. Moving panels hide his kitchen, closet, bathroom, dining room and living room, and the bed is stored under the terrace balcony that overlooks the city of Barcelona.

This 196 square-foot home cost its architect less than $12,000 to build.

Image credit: Macy Miller

Size: 196 sq. ft.

Location: Boise, Idaho

Boise architect Macy Miller decided to downgrade from a full-size home to a tiny one, which she designed and built herself. She lives there now with her partner and dog.

The home, which sits on top of a flatbed trailer, cost about $11,500 all in. The most expensive component is the composting toilet -- about $2,000 -- which uses barely any water.

A California couple also built their 170 square-foot home on a flatbed trailer.

Image credit: Alek Lisefski

Size: 170 sq. ft.

Location: Sebastopol, California

Web designer Alek Lisefski and his girlfriend fulfilled their dream of a simpler, more minimalist life by building a smaller home. The project took about a year and cost them $30,000. In the end they wound up with a small mobile home measuring about 2,261 cubic feet.

The home doesn't feel cramped, thanks to the 13-foot ceilings, fold-away furniture, and smaller appliances with dual purposes.

A Yale student built a 144 square-foot environmentally-friendly home instead of living in traditional student housing.

Image credit: Michael Janzen via YouTube

Size: 144 sq. ft.

Location: New Haven, Connecticut

When Elizabeth Turnbull was accepted into Yale's Graduate School of Forestry and Environmental Studies, she built her own 144 square-foot tiny house instead of opting for university housing.

During the building process, Turnbull made sure to keep in mind the environmental impact her home would have and to minimize any potentially harmful effects by using all FSC-certified wood, non-toxic paints and finishes, and recycled windows.

A Colorado couple built this 124 square-foot home that has a kitchen, bathroom and sleeping loft.

Image credit: Kevin Hoth

Size: 124 sq. ft.

Location: Colorado

Colorado couple Christopher Smith and Merete Mueller began building their home back in 2011 and documented the journey in a new movie called "TINY: A Story About Living Small."

The house has a small galley kitchen, a bathroom, and a sleeping loft nestled between the floor and the 11-foot-high ceilings. For storage, the couple makes use of a small closet and two built-in bookshelves, and works from a built-in desk a reclaimed hardwood table.

This 112 square-foot mobile house traveled across 9,000 miles.

Image credit: OutdoorResearch via YouTube

Size: 112 sq. ft.

Location: Mobile around the U.S. and Canada

Zach Griffin and four friends decided to take an epic, cross-continental ski trip, and built a 112 square-foot mobile pod house where they lived for the six week, 9,000 mile-long trip.

The tiny house has a “drawbridge” bunk bed that comes down from the two-person sleeper loft, and a pull-out sofa bed. The skiers relied on the kindness of hostels and strangers for bathrooms, as the pod has none. It does, however, have electricity, a generator, and a toaster oven and propane stove as their kitchen.

They even made a movie about their trip in their tiny, temporary home.

This 104 square-foot home is beautifully designed.

Image credit: Chris and Malissa Tack

Size: 104 sq. ft.

Location: Seattle, Washington

Chris and Malissa Tack built their 104 square-foot home just outside of Seattle. They had both been working in the tech industry and decided to leave their complicated, material lives behind and make a clean break, starting with a smaller, simpler home.

The home has cut their living cost substantially, and they predict the home will be paid in full in just two or three years. Chris Tack, who now works as a photographer, has taken many beautiful photos of the home, which has a kitchen, living and dining area, bathroom, storage area, and sleeping loft.

This 100 square-foot environmentally-friendly house will actually earn you money.

Image credit: thehypnoguy1 via YouTube

Size: 100 sq. ft.

Location: Edinburgh, Scotland

This home is called the "Eco-cube." At 10 cubic feet, it's still sizeable enough to hold a small living room, dining area, kitchen, washer and dryer, a closet, full shower, toilet and full-sized bed.

It was designed by Dr. Mike Page of the University of Hertfordshire and founder of the Cube Project, an initiative created to prove that a person could "live a comfortable, modern existence with a minimum impact on the environment." With solar panels, the Eco-cube can earn you $1,600 a year through the UK’s feed-in tariff.

This 89 square-foot home has an "entertainment area," a kitchen, and even a fireplace.

Image credit: screenshot via YouTube/Fair Companies

Size: 89 sq. ft.

Location: Sebastopol, California

Jay Shafer is the founder of the Tumbleweed Tiny House Company, which constructs small homes ranging from 65 to 874 square feet.

Shafer's own tiny house, at 89 square feet, has an "entertainment area," a kitchen with plumbing, a working fireplace, shower and toilet, lofted bed, and shelves on almost every wall.

This 84 square-foot home cost just $10,000 to build, and even less to maintain.

Image credit: radley87 via YouTube

Size: 84 sq. ft.

Location: Olympia, Washington

Dee Williams returned from an eye-opening trip to Guatemala and decided to downsize her home from 1,500 square feet to just 84 square feet. She moved out of her big house, built a small one from scratch, and parked it in her friend's backyard.

This home, which she calls "The Little House," cost about $10,000 to build, and even less to maintain. With a propane tank for heat and solar panels for electricity, Williams pays very little to live there.

Famed architect Renzo Piano jumped into the tiny homes business with these 79-square-foot German models.

Image credit: Ariel Huber for Vitra

Size: About 79 sq. ft.

Location: Weil am Rhein, Germany

Best known for Manhattan's New York Times Building, London's The Shard, and the Paris' Pompidou Museum, now Piano is turning his attention to the tiny details -- specifically, to "Diogene," a tiny house prototype built for German furniture company Vitra.

The house, constructed of wood and aluminum paneling, collects, cleans, and reuses water; it also supplies its own power, and features photovoltaic cells and solar modules, a rainwater tank, a biological toilet, and natural ventilation.

The owner of this 75-square-foot house in Rome rents the space to friends and tourists.

Image credit: Photo by Matteo Rossi

Size: 75 sq. ft.

Location: Rome, Italy

Architect and designer Marco Pierazzi saw the potential in an abandoned, one-room alleyway house just steps from Roman landmarks like the Pantheon and Saint Peter's Square. He bought it, fixed it up, and lived there with his wife until their child was born.

While it's not commercially available, Pierazzi now rents what he calls the "smallest house in Italy," making it a convenient place to stay on a Roman holiday. All the comforts of home, the little house has a full kitchen, a bathroom with a shower, a small lofted sofa bed, and an LED TV with Hi-Fi sound system.

A student-built 70 square-foot home in Vermont is completely sustainable.

Image credit: Inhabitat

Size: 70 sq. ft.

Location: Poultney, Vermont

In a renewable entergy and ecological design class at Green Mountain College, a group of students designed a stunning and creative mobile shelter that gives back to the earth.

They called their home OTIS (Optimal Traveling Independent Space), a 70 square-foot, solar-powered dwelling made of all reclaimed materials. The home has a sleeping area, and has the ability to collect and recycle rainwater.

This 60 square-foot home is the smallest house in the UK.

Image credit: mel vyn via YouTube

Size: 60 sq. ft.

Location: Conwy, Wales

Also known as the Quay House, this tiny red home, which measures just 10 feet by 6 feet, is known as the smallest house in the U.K., and has actually become a tourist attraction in Conwy, Wales.

The home has been occupied by various people since the 16th century, including a 6-foot-3-inch fisherman. The house has room for a stove, water tap, bed, and bedside storage.

This five foot-wide home in Poland is possibly the skinniest apartment in the world.

Image credit: Inhabitat

Size: 46 sq. ft.

Location: Warsaw, Poland

This 46 square-foot apartment in Warsaw, Poland, is just five feet wide, possibly making it the skinniest apartment in the world.

Polish architect Jakub Szczesny sandwiched the tiny home in an alley between two other buildings. With no windows, a microscopic fridge, and a shower that aims almost directly over the toilet, this place is as small as they come. The kitchen table has room for two chairs, and the fridge has room for just two sodas.

This small home in China is built on top of a tricycle.

Image credit: People's Architecture Office

Size: About 33 sq. ft. when folded

Location: Beijing

Beijing’s People’s Architecture Office and People’s Industrial Design Office designed and built a polypropylene mobile home so small that it can be folded up, accordion-style, and carted around on the back of a tricycle.

The expandable home can attach to others for more space, or to portable gardens to give the appearance of a “yard.” Facilities in the house include a sink, stove, bathtub, and water tank. All the furniture is convertible: the bed becomes a dining table, the countertop becomes a bench for seating, and it can all fold up into the front wall.

This 15 square-foot bike camper home was designed to be a residence for the Burning Man Festival.

Image credit: Paul Elkins via YouTube

Size: About 15 sq. ft.

Location: Black Rock Desert, Nevada

Designer Paul Elkins needed a convenient and eco-friendly way to get around during the Burning Man Festival, so he designed a wind turbine-powered bicycle camper that functions as a bedroom, living room, and kitchen. It's even equipped with a solar-powered oven.

As for the bathroom, you'll have to resort to the great outdoors for that.

This 11 square-foot home in Berlin is dubbed the "world's smallest house."

Image credit: CNN via YouTube

Size: 11 sq. ft.

Location: Berlin

Architect Van Bo Le-Mentzal built a one square-meter (11 square-foot) house which is light enough to pull on its wheels, and provides just enough room to sit or lie down and sleep (but only when tilted on its side).

Le-Mentzal says he designed the structure not as a way to address homelessness or create a new kind of emergency shelter, but as a thought experiment to make people think about the way they define the concept of "home."

However, that hasn't stopped governments and private citizens all over the world from contacting him about the plans.

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