The maze
Build a simple maze inside the dish from narrow strips of plastic or card. Put the blob at one entrance and an oat flake at the exit. It fills every corridor first, then withdraws from the dead ends.
Topic page
The BlobPhysarum polycephalum
No brain, no mouth, no eyes — and yet it finds the shortest way through a maze. The blob is a single cell that grows bigger than your hand. In 2019 the Paris Zoo put it on display like an animal, and since then it has been turning up in classrooms and on kitchen tables.
This page explains what the blob really is, how to keep one at home, which experiments actually work — and what to do when something goes wrong.
13 seconds of time-lapse, real footage. A sclerotium wakes up on the growing medium and spreads its network of veins — in real time this takes about two days. Footage: Mister Blob.
- What it is
- A single cellwith millions of nuclei — neither animal nor plant nor fungus
- Speed
- up to 4 cm/hourfaster than any plant grows
- Sexes
- around 720three gene groups with up to 16 variants each
- Brain
- noneno nervous system, no organs
- Food
- Porridge oatsin the wild bacteria, yeasts and fungal spores
- Temperature
- 18 – 25 °Cin shade, never in direct sun
- Dormant form
- Sclerotiumkeeps virtually indefinitely when dry
- Injury
- heals itselfcut in two, it grows back together within minutes
What it is
Neither animal nor plant nor fungus
The blob is filed under slime moulds, but a mould it is not. It belongs to a group of its own that branched off early from animals, plants and fungi. That is why it fits none of the boxes we were taught at school.
The most astonishing part is how it is built: what you see in the petri dish is one single cell. It simply has no internal walls and no single nucleus, but millions of them drifting in shared cytoplasm. The Latin name says as much — polycephalum means «many-headed».
This cell moves by pumping its own contents around. Inside the yellow network the cytoplasm streams back and forth every few seconds, a little like a heartbeat without a heart. Where there is food, the veins thicken; where there is nothing to gain, they are dismantled. That thickening and dismantling is the whole trick behind its route-finding.
And it has two states. Moist and well fed, it is a plasmodium: the bright yellow network that grows and travels. As things dry out it contracts into a sclerotium — a hard, brownish crust. In that form it survives for years. A drop of water and a few oats, and it carries on where it left off.
Research
The single cell that plans rail networks
The blob would have stayed a footnote in biology had it not started solving problems no one expects of a creature without a nervous system. Four results made its name.
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2000
It solves a maze
At Hokkaido University, Toshiyuki Nakagaki places a blob in a maze and puts food at two exits. The blob first fills every corridor, then withdraws from the dead ends, and in the end leaves a single vein standing: the shortest connection between the two food sources. Published in Nature.
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2008
Ig Nobel Prize
The same discovery earns the team the Ig Nobel Prize in Cognitive Science — the award for research that «first makes people laugh, then makes them think».
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2010
It rebuilds the Tokyo rail network
Atsushi Tero lays out oat flakes in the pattern of the cities around Tokyo and places a blob where Tokyo sits. The network that emerges resembles the real railway system remarkably closely — at comparable total length, efficiency and fault tolerance. Published in Science; a second Ig Nobel Prize follows.
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2016
It learns — and passes it on
Audrey Dussutour's group in Toulouse puts bitter substances such as caffeine and quinine in the blob's path. At first it avoids them; after a few days it simply walks through: habituation, a recognised form of learning. And more than that — when a habituated blob fuses with an inexperienced one, the newcomer inherits the experience.
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2019
It goes to the zoo
In October 2019 the Paris Zoo puts it on show in a vivarium of its own and gives it the name everyone knows it by today: le blob — after the 1958 science-fiction film.
Care
How to keep a blob
A blob needs less looking after than a houseplant. It has four settings — get those right and the rest takes care of itself.
18–25 °C
Temperature
Ordinary room temperature. Below 15 °C it turns sluggish, above 30 °C it goes to sleep.
Shade
Light
It avoids direct sun. A cupboard or a drawer suits it best.
moist
Medium
Agar holds water evenly — steadier than damp paper and slower to dry out.
sparing
Food
A few oat flakes. Only add more once the old ones are gone.
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Prepare the medium
Dissolve the agar in hot water as instructed, pour it into the petri dish and let it cool completely. The surface should set like a firm jelly — not liquid, not dry.
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Wake the blob
Place the sclerotium in the middle of the medium with the tweezers, moisten it with a few drops of water and put two or three oat flakes beside it — not on top, but a short distance away. Lid on, keep it dark.
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The first hours
After two to twelve hours the first yellow edge appears. From then on it moves quickly: overnight, half the dish is covered by a network of veins. Condensation on the lid is normal — a quick airing is enough.
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Feed and keep clean
Replace oat flakes once they are eaten and remove leftovers. Overfeeding is the most common mistake: whatever is left behind will go mouldy. Rinse and dry the tweezers before each intervention.
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Put it to sleep
Want a break? Simply stop watering. The blob dries out slowly and contracts into a sclerotium. Keep it dry and cool — and wake it again weeks or months later.
Going away? No problem.
The blob is the only pet you can put in a drawer before a holiday. Let it dry, take it with you or leave it behind, moisten it when you return — it carries on where it left off.
Experiments
Six experiments that work at home
Watching is lovely, but the blob only gets really interesting once you set it tasks. These six need nothing beyond the kit, some oats and a little patience.
The taste test
Lay three different things around the blob at equal distance — an oat flake, a piece of cucumber, a piece of tomato. Which does it reach for first, which does it ignore? Write the result down and compare with others.
The light test
Cover one half of the dish with card and put it somewhere bright — not in direct sun. The blob migrates into the dark half. No eyes, no nerves, and still a clear decision.
The reunion
Divide the blob in two with clean tweezers and put the halves back a few centimetres apart. Both keep growing — and when they meet, they fuse back into a single organism.
The map of Switzerland
Lay oat flakes on the medium where Zurich, Basel, Bern, Geneva and Lugano sit on the map, and put the blob on Zurich. Then compare its network with the Swiss railway map. This same experiment, with Tokyo, won an Ig Nobel Prize in 2010.
Your own time-lapse
Phone on a tripod or a stack of books, interval shots every two minutes, lighting kept constant. After one night you have your own film — and you see movements that stay invisible to the naked eye.
Troubleshooting
When something goes wrong
Almost everything that can go wrong can be fixed. The most common cases:
- White or green patches on the medium
- Mould. Cut the affected part away generously, or move the blob to fresh medium with clean tweezers. Cause: too much food or unclean tools. Feed less, remove leftovers consistently.
- The blob will not wake up
- Give it more time — up to 48 hours is normal. Check temperature and moisture, and put a fresh oat flake beside it. Cause: too cold, too dry, or the medium has already dried out.
- Patches turn transparent or pale
- Not a fault, but a trail. Wherever it has already been, the blob leaves a thin layer of slime — that is how it «remembers» explored ground and avoids going there twice. Nothing to do.
- It heads for the rim, or out of the dish
- Add food and move the dish somewhere darker. Put the lid back on. Cause: nothing left to eat, too bright or too warm.
- It turns brown, hard and shrinks
- Do not throw it away. This is the sclerotium, its normal resting state. Store it dry and wake it up later. Cause: the medium has dried out.
- Condensation on the lid
- Take the lid off briefly, wipe it, put it back. Entirely normal and harmless to the blob.
Safety
The blob is harmless to people and pets. Even so, the agar and the oats are part of the experiment and not for eating. Younger children are best supervised — and wash your hands afterwards, as you would in a lab.
Frequently asked
What people ask most
How long does a kit keep before I open it?
Indefinitely. The blob ships asleep, as a sclerotium. As long as it stays dry, it waits until you feel like starting. There is no expiry date — a kit can sit in a cupboard for a year without trouble.
Is the blob dangerous?
No. Physarum polycephalum is harmless to people and pets and is not infectious. It lives on oats and micro-organisms, not on us. Neither the blob nor the medium should be eaten.
What age is it suitable for?
From primary school age, and younger with help. Waking the blob is simple enough for children, and the watching grips adults just as much. In schools it is used from middle school up to upper secondary.
How long does the experiment last?
That is up to you. You see the waking and the growth in the first few days. Well looked after, the blob lives for months. If you want a break, put it to sleep and wake it again later — as often as you like.
What language are the instructions in?
The printed booklet in the kit is in French and English. The QR code inside leads to further language versions, including German and Italian. The kits are made in France.
Does the blob need a holiday sitter?
No. Stop moistening it before you leave and it will dry into a sclerotium by itself. When you return, put it on fresh medium, moisten, feed — done.
Can it escape from the dish?
It can crawl over the rim if it runs out of food or the light bothers it. Away from the moist medium, though, it dries out and crusts over quickly — it will not cause any harm.
Can I propagate it or give it away?
Yes. Cut a piece off and place it on its own medium — both parts live on. Dried sclerotia can be sent in an envelope.
For schools and classrooms
The blob makes a rewarding teaching subject: alive, harmless, pausable at any time and storable in any drawer. For class sets, purchase on account and individual quotes we have a page of its own.
Grow your own
The blob growing kit
The kit comes from Mister Blob in Montenach, Lorraine, and is made in France. It contains everything you need to start — the blob travels asleep as a sclerotium and waits until you wake it.
Mister Blob · Made in France
Blob Breeding Set Malu
The «Malu» strain is robust and grows briskly — a good choice for your first blob.
- 2 sclerotia — the blob in its dormant state
- Agar for the growing medium and oat flakes for food
- Petri dishes, pipette and tweezers
- Illustrated instructions, printed FR/EN, plus DE and IT via QR code
CHF 29.95
View productIn stock in Kriens — order by 5 pm and it ships the same day.
More natural wonders to grow
Anyone who gets hooked on watching will find more kits here that follow the same principle: set it up, wait, marvel.
Sources and further reading
- Nakagaki, Yamada & Tóth: Maze-solving by an amoeboid organism. Nature 407, 2000.
- Tero et al.: Rules for Biologically Inspired Adaptive Network Design. Science 327, 2010.
- Boisseau, Vogel & Dussutour: Habituation in non-neural organisms: evidence from slime moulds. Proceedings of the Royal Society B 283, 2016.
- Vogel & Dussutour: Direct transfer of learned behaviour via cell fusion in non-neural organisms. Proceedings of the Royal Society B 283, 2016.
- Parc Zoologique de Paris: «le blob» exhibit, from October 2019.
- Husbandry notes and images: misterblob.com, Montenach (F).
Mister Blob was founded by the biologist Morgane, out of a fascination with living things and their curiosities. The kits make observing Physarum polycephalum at home possible for everyone — for children and adults alike.