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Short answer: an organoid is a tiny, self-organized, three-dimensional tissue culture grown from cultured cells or tissue samples. It can reproduce much of the complexity of an organ, or only selected aspects of one (NCATS Toolkit definition). It is a research model, not a transplantable organ, and the published literature is clear about what it lacks.
This guide is for researchers and lab staff who need to know what the term covers, where it came from, and which gaps to plan around before choosing an organoid model.
What is an organoid? Definition and scope
The NIH NCATS Toolkit glossary describes organoids as tiny, self-organized, three-dimensional tissue cultures derived from cultured cells or tissue samples, which can replicate much of the complexity of an organ or only selected aspects of one. Two parts of that definition matter in practice. Self-organized means the structure arises from the cells themselves rather than being assembled by hand. Selected aspects means that an organoid is a model of some organ features, not a miniature organ.
Searches for “organoids”, “organoid definition” and “what is an organoid” all point at this same concept.
Who discovered organoids?
No single date marks the idea of growing tissue in three dimensions, but a widely cited early landmark is Sato et al., Nature 2009 (“Single Lgr5 stem cells build crypt-villus structures in vitro without a mesenchymal niche”, PMID 19329995). The paper reports a long-term culture system in which intestinal crypts form crypt-villus organoids containing all the differentiated cell types, and in which a single sorted Lgr5-positive stem cell can initiate the culture. Its conclusion is that intestinal crypt-villus units are self-organizing structures that can be built from a single stem cell without a non-epithelial cellular niche.
How organoids are made and used in practice
Organoids start from stem cells or from tissue samples and are grown in an extracellular matrix, a three-dimensional support in which the cells organize themselves (Li et al., Cell Regeneration, 2020). Patient-derived organoids are the basis of the “personalized medicine” literature, where tissue from an individual is cultured so that the model reflects that source.
What can you do with organoids? What are the benefits?
- Model an organ or disease in human-derived cells in three dimensions, rather than in a flat monolayer.
- Study tissue from a specific source, including patient-derived samples (Li et al., 2020).
- Support replacement of animal testing as one of the human-cell-based approaches discussed under the 3Rs; see the CASRAI guide to the FDA Modernization Act 2.0 and the research animal term.
- “Beyond monolayers: a comparative analysis of 2D cell cultures and 3D in vitro models as new approach methodologies.” Front Bioeng Biotechnol 2026. PMC13548193 (read 2026-11-07).
Organoids vs organs-on-chips: are they the same thing?
No. An organoid is defined by self-organization of cultured cells (NCATS). An organ-on-a-chip is a different platform: an engineered device, often described with the NCATS term “tissue chip”, rather than a structure the cells build for themselves. The two are sometimes combined in the literature, which is why the terms get blurred. The CASRAI guide to organ-on-a-chip as a replacement method covers the chip side.
Organoid vs spheroid: what is the difference?
Both are three-dimensional cultures, but they are defined differently. A 2026 comparative review (Frontiers in Bioengineering and Biotechnology) describes spheroids as “tightly compacted spherical multicellular aggregates” formed by the self-assembly of cells under non-attachment surface conditions, with size and compactness as the key parameters. It describes organoids as self-organized, multicellular 3D culture models derived from embryonic, adult or induced pluripotent stem cells, formed by differentiation and self-organization, that aim to recreate specific organ functions and recapitulate organ microanatomy.
The same review states that organoid development requires longer and more complex protocols (weeks to months) than spheroid culture, and that organoids provide more biological fidelity to organs or tissues. Which model fits an experiment depends on the question; this page does not rank them.
Do organoids have blood?
No. A review of patient-derived organoids states that cultures cannot mimic interactions with vasculature and stroma, and that nearly all patient-derived organoid types lack stroma, nerves and vasculature (Li et al., 2020). Anything that depends on blood supply, nerve input or surrounding connective tissue is therefore outside what a standard organoid can show.
Limits checklist for planning an organoid experiment
Each line below traces to Li et al., Cell Regeneration 2020, as read on 2026-11-07.
| Question to ask before relying on an organoid model | What the source states |
|---|---|
| Does my question involve blood vessels, nerves or connective tissue? | Nearly all patient-derived organoid types lack stroma, nerves and vasculature. |
| Does it involve interactions with vasculature or stroma? | Organoid cultures cannot mimic these interactions. |
| Do I need large quantities of one culture? | The air-liquid interface method is described as having limited expansion. |
| Do I plan genome editing? | Variable experimental conditions limit the efficiency of genome editing in organoids. |
For wider cell-culture practice, see the CASRAI guide to trypsinization, the dissociation step used when passaging adherent cultures, and the overview What is cell biology?
Why are organoids controversial? Can brain organoids suffer?
The controversy centres mainly on human neural organoids. The 2021 National Academies report The Emerging Field of Human Neural Organoids, Transplants, and Chimeras: Science, Ethics, and Governance examines organoids, transplants and chimeras. Among the questions it poses are how large or complex brain organoids would need to be to reach awareness, and whether patients should give explicit consent for their cells to be used to create neural organoids.
Whether a brain organoid can suffer is therefore an open question under study, not a settled finding in either direction. The practical issues the report raises, consent for donated cells and governance of the most complex neural models, apply to institutions that handle such work.
Common misunderstandings
- “An organoid is a small organ.” The NCATS definition says it may replicate only selected aspects of an organ.
- “An organoid is an organ-on-a-chip.” They are separate platforms (see above).
- “Organoids include blood supply.” Most patient-derived types lack vasculature, stroma and nerves.
FAQ
What is an organoid?
A tiny, self-organized, three-dimensional tissue culture from cultured cells or tissue samples that replicates much or selected aspects of an organ (NCATS Toolkit).
Who discovered organoids?
Sato et al. (Nature, 2009) reported intestinal crypt-villus organoids built from single Lgr5 stem cells, a landmark early report.
What is the difference between an organoid and a spheroid?
A spheroid is a compact spherical aggregate of cells that self-assembles under non-attachment conditions; an organoid is a stem-cell-derived culture formed by differentiation and self-organization that aims to recreate organ microanatomy and function. Organoid protocols are longer and more complex, taking weeks to months (2026 Front Bioeng Biotechnol review).
Do organoids have blood?
No. Nearly all patient-derived organoid types lack vasculature, along with stroma and nerves (Li et al., 2020).
Are organoids and organs on a chip the same?
No. Organoids self-organize from cells; organs-on-chips are engineered devices.
Can brain organoids suffer?
This is an open question that the 2021 National Academies report addresses through questions about the size and complexity at which awareness might arise.
Sources
- NIH NCATS Toolkit, “Organoid”: toolkit.ncats.nih.gov/glossary/organoid (read 2026-11-07).
- Sato T, et al. Single Lgr5 stem cells build crypt-villus structures in vitro without a mesenchymal niche. Nature 2009. PMID 19329995 (abstract read 2026-11-07).
- Li et al. Organoid based personalized medicine: from bench to bedside. Cell Regeneration 2020. PMC7603915 (read 2026-11-07).
- National Academies of Sciences, Engineering, and Medicine (2021). The Emerging Field of Human Neural Organoids, Transplants, and Chimeras: Science, Ethics, and Governance. nationalacademies.org/publications/26078 (read 2026-11-07).
