Fold paper. Insert lens. This $2 microscope changes how kids see the world

Eight-year-old S. Hariraj is a Foldscope devotee.

He's used it to look at the milk from the cows his parents raise. Though the milk looks creamy, the Foldscope reveals a world of microorganisms. "It has to be boiled and cooled before we can drink it," he says. "The Foldscope taught me that the world we see around us can be very different than what we assume. It's like having a third eye."  

The 8-year-old is talking about a device that is a fully functional paper microscope.

Everything you need to construct the Foldscope comes in a pouch: a sheet of paper with four main parts to punch out to build the microscope. They're waterproof and tear-resistant — it's a similar paper to that used for currency notes.

The main part of the Foldscope is one long sheet of paper. Half of this is blue (that's the front portion) and the other half is yellow (which you fold to become the back of the foldscope). Magnets stick to each end, holding front and back together. There's a lens in the pouch — and a hole to indicate where it should go.

Once assembled the Foldscope is the size of a bookmark. It's small enough to fit in a pocket and can magnify up to 140 times.

Each unit costs around $2 to make. Foldscopes are offered for free to kids in lower income countries; various upgraded models with extras are sold as well, earning money for the charitable endeavor.

The Foldscope is the invention of MacArthur genius grant winner, Manu Prakash, and his colleague Jim Cybulski. It made its debut ten years ago. And as young Hariraj observes, it is a game-changer.

The inspiration came when Prakash, 44, was growing up in the northern Indian city of Meerut. Now an associate professor in the Department of Bioengineering at Stanford University, he recalls an afternoon in Grade 6 when he and his classmates were stumped by a single test question.

"We were asked to draw a microscope," he says. "None of us could because we just hadn't seen one."

Microscopes were expensive, and not all schools could afford a well-equipped lab.

"Growing up, I knew that the spirit of exploration was critical to the study of science," says Prakash. "But in order to develop that spirit, you have to have the right kind of tools. And for many, access is impossible."

Over the years, Prakash experimented with building microscopes, even stealing lenses from his brothers' eyeglasses.    

In 2014, at Stanford, he collaborated with a Ph.D. student in his lab -- Jim Cybulski -- and together, they created a microscope by using origami or folding techniques to combine paper and a basic lens.

The end product was portable and much less fragile than a regular microscope. Yet it can do exactly what a microscope does: bring a much closer eye to the tiny intricacies of the world.

Over the next two years, the colleagues built 50,000 Foldscopes — they cost less than $1 apiece to make at the time. They intended to ship them for free to kids in 130 countries. Shipping costs did add up. Their initial funding of $147,875 came from a 12-month grant from the  Gordon and Betty Moore Foundation.  

There are now three different variations of the paper product, with 140 times magnification as the base, 340 times for older students and researchers, and as of this year a mini with 50 times magnification for kids as young as 4 or 5.  

Today, anyone can go online to purchase a Foldscope from Prakash's website for $1.75. Kits for educators and parents include different accessories: an LED light, multiple lenses, explorer cards for recording observations. The kits cost in the $40 to $50 range; proceeds go to help ship Foldscopes to children in low-income countries, says Prakash. So far, he says, they've distributed 2 million units in 180 countries.

Zooming in on ants and pollen

Young Hariraj encountered the Foldscope at Eden School in the southern Indian city of Madurai. On a recent fall afternoon, Indira Pandiarajan, the school principal and a social studies teacher, smiles at the excited faces of the 50 children, ages 6-11, sitting cross legged in a circle around her.

"It's time to take out your Foldscopes," she says. The kids cheer and clap, then rush up to their school bags and pull out what appears to the untrained eye to be a folded piece of paper. They've used it to examine everything from ants to leaves to flower pollen.

Building communities of Foldscope users has been as much of a priority as building distribution networks, says Prakash. That's how he met Mo Pandiarajan, a mathematics teacher and founder of Eden school. Pandiarajan had sent Prakash a short email with a spreadsheet attached that described the ways he'd used Foldscope — with thousands of entries, including parties at weddings and close-up of bugs on fruit at local markets.

Mo Pandiarajan established Eden School in 1998, renovating his parents' modest two-story home. The school, in rural Muthupatti, is surrounded by lush green fields and brown sand. Sixty-seven students from kindergarten to grade 5 currently study here; most are first generation learners from low-income families, who pay a small tuition fee.

Activities using the Foldscope are an integral part of learning at Eden. Once the students have retrieved their Foldscopes from their bags, a teacher leads them out of the classroom. Under her watchful eye, over the next 20 minutes, the children rush about, looking for specimens to view through their microscopes. Some of them gently scoop up bugs — spiders, ants and grasshoppers. Others go for leaves, sticks and blades of grass.  

Pandiarajan helps the younger ones open the flaps of their Foldscopes, place their chosen specimens on top of the sticky transparent slide compartment.

Committed to popularizing science education, in 2015, Pandiarajan and his wife set up the Eden Science Club for the students of Eden school. The following year, he became one of four Foldscope fellows across India after his initial interaction with Prakash.      

Over the years, Prakash give him over 4,000 free Foldscopes to distribute as he saw fit. Each kid at Eden school gets one, and he's handed them out at workshops across India. With support from the government, philanthropists and charities, India has received half a million units.   

What kids — and researchers — see

Eight-year-old S. Hariraj has been using the Foldscope for 2 years now.

The first creature he examined was an ant: "I couldn't believe how beautiful it was." He says he uses the Foldscope everyday and it always teaches him something new.

Ramana Rajeesh Kumar, age 11, Meenakshi, 8, and Magathi Yazhini, 9, say they take their Foldscopes everywhere they go so they can whip them out in case they spot something interesting.

Ramana has been fascinated with bugs for a while. "They look even cooler under the Foldscope," he says. "Especially their eyes and hairy feet!"  

Magathi enjoys magnifying pollen grains. "They look like powder, but under the Foldscope, you can see all these amazing shapes — and they're split into what looks like tiny rooms," she says.  

Meenakshi likes to examine the leaves the most. "It was so exciting to see the tiny pores on the leaf called stomata," she says. "It made me think -- wow, so that's how plants breathe."  

Ramana and Magathi have moved to a new school for sixth grade. The first thing they realized was that using the Foldscope wasn't the norm in most other schools. "Everyone in our old school has a Foldscope in their pockets. In our new school, no one even knows about it. That made me sad," Ramana says.  

And though he's settled into the new school routine, Magathi says she feels like something is missing. "With my old classmates, I was always comparing notes. What did you see today? Was it more extraordinary than what I saw? I miss that kind of talk."

And it's not just for amateurs. Some 1,400 research papers have referenced the Foldscope. Karthik Balasubramaniam, a scientist at the Agharkar Research Institute at Pune, says the Foldscope has helped make his fieldwork easier. He studies a microscopic kind of algae, collecting water samples from across the country to assess biodiversity and pollution.

"Carrying an expensive microscope onto the field to study each water sample can be hard," he says. "The Foldscope isn't as powerful as a lab microscope. But it can let me see whether my water sample has diatoms [the microscopic algae] or not."

And it's a lot of fun on impromptu trips. Former students from Eden school plan picnics and short trips where they can teach their own kids to observe the world around them with the Foldscope.

"I just love the look of amazement when anyone looks into the Foldscope for the first time, particularly little kids," Pandiarajan says. "When their eyes light up, I know that's the moment they will embrace science and learning for the rest of their lives."

Kamala Thiagarajan is a freelance journalist based in Madurai, Southern India. She reports on global health, science, and development, and her work has been published in the New York Times, The British Medical Journal, BBC, The Guardian and other outlets. You can find her on X @kamal_t