A supply problem
In the United States alone, more than 100,000 people are on the national transplant waiting list, and the US Health Resources & Services Administration reports that 17 die each day waiting for an organ that never arrives.
Tissue engineering · Regenerative medicine
3D Organ Printing
Printers that build living tissue layer by layer, one cell at a time. Here is what bioprinting can actually do today, what it cannot do yet, and who is working on it.
The basics
What is 3D organ printing?
A technology that could one day end the transplant waiting list — and that already quietly powers a good deal of drug testing.
Printing with cells instead of plastic
3D bioprinting works like ordinary additive manufacturing: a digital model is sliced into layers, and a machine lays those layers down one at a time. The difference is the material. Instead of molten plastic, a bioprinter deposits bioink — living cells suspended in a water-rich gel that supports them while they knit together.
The printed construct then moves to an incubator or bioreactor, where the cells reorganise, start producing their own matrix and mature into something that behaves like real tissue. Where the cells come from matters enormously: tissue grown from a patient's own cells carries far less risk of immune rejection than a donated organ.
Real progress
Skin, cartilage, bone, cornea and blood-vessel grafts have reached patients or late-stage trials. Whole hearts, kidneys and livers have been printed at small scale in laboratories, but none is anywhere near transplantable.
Useful long before transplants
Bioprinted liver, kidney and tumour tissue is already sold as a testing platform. Human tissue in a dish predicts toxicity better than animal models, which is why pharmaceutical companies became the industry's first paying customers.
Milestones
What has been bioprinted so far
Every tile below is a genuine laboratory or clinical result. The status label tells you how far it has actually travelled — most of this work is still pre-clinical.
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ResearchHeart
Cell-sized cardiac constructs that beat in a dish, and full-scale collagen scaffolds.
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ResearchKidney
Printed nephron-like tubules and organoids used for drug toxicity testing.
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Pre-clinicalLiver
The first bioprinted tissue sold commercially, as a drug-testing model.
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In patientsSkin
The closest to routine clinical use, including printing directly onto a wound.
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Pre-clinicalCornea
Printed in minutes from collagen and stem cells; several groups are heading for trials.
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In patientsEar
An implant grown from a patient's own cartilage cells was placed in 2022.
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ResearchOvary
A printed scaffold seeded with follicles restored fertility in mice.
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OverviewEverything else
Bone, cartilage, blood vessels, trachea, nerve and pancreatic tissue.
How it works
From a scan to living tissue
Four stages separate a medical image from a piece of functioning tissue.
1. Model
A CT or MRI scan of the patient is converted into a 3D model, then sliced into printable layers and a toolpath. Getting the internal architecture right matters more than the outer shape.
2. Prepare the bioink
Cells — often stem cells taken from the patient — are expanded in culture and mixed into a hydrogel such as gelatin, collagen or alginate. The gel must be soft enough for cells to survive and stiff enough to hold its shape.
3. Print
Extrusion, inkjet, laser-assisted or light-based printing deposits the bioink layer by layer, often alongside a sacrificial material that is later washed out to leave open channels for blood vessels.
4. Mature
The construct goes into a bioreactor that supplies nutrients, oxygen and mechanical stimulation. This maturation stage takes days to weeks and is where most attempts fail.
The industry
Companies working on bioprinting
Twenty-four organisations building printers, bioinks and tissue products. Logos link to the company's own site.
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Common questions
3D organ printing, briefly answered
Has a 3D-printed organ ever been transplanted into a human?
Simple printed tissues have — skin grafts, cartilage, bone and a printed ear implant placed in 2022. No solid internal organ such as a heart, kidney or liver has been printed and transplanted. Those remain laboratory work.
Why is it so much harder to print a kidney than skin?
Thickness. Cells more than roughly 200 micrometres from a blood supply starve, so any tissue thicker than a sheet of paper needs its own vascular network. Skin is thin and flat; a kidney contains around a million filtering units fed by kilometres of vessels. Building that plumbing is the field's central unsolved problem.
How long until printed organs are available to patients?
Simple flat and tubular tissues are already in trials and should broaden over the next decade. Researchers in the field generally place transplantable solid organs decades away, and treat any shorter estimate with caution.
Would a printed organ be rejected by the immune system?
That is the main reason to print at all. If the tissue is built from the patient's own cells it is genetically their own, so the lifelong immunosuppressant drugs that transplant recipients depend on may not be needed.
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