Brain organoids

Also known as Cerebral organoids, Cortical organoids, Neural organoids

Brain organoids are small three-dimensional clumps of brain-like tissue grown from human stem cells. They are used to model brain development and disease, and some have been transplanted into rat brains, but they remain small, lack blood vessels and do not yet show the learning that 'organoid intelligence' proposals describe.

Lab demonstrationDemonstratedReviewed 21 Oct 2026
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

In plain language

A brain organoid is a small ball of brain-like tissue grown in a dish from human stem cells. The cells are coaxed to form layers and cell types that resemble parts of the developing human brain, such as the outer layer of the cortex. Scientists use them to study how the brain forms and what goes wrong in some conditions, because they can be grown from a person's own cells.

Brain organoids are not small brains, and they do not think or sense the world. They lack the blood vessels, wiring and inputs that a real brain has, and they vary from one organoid to another. Researchers therefore treat them as models that can show some features of human brain tissue, not as copies of a whole brain. Some studies have also placed organoids into rat brains to see how they develop inside a living host.

Technical explanation

Lancaster and colleagues (2013) grew three-dimensional organoids from human pluripotent stem cells. They formed distinct brain regions, including a cortex-like region that produced mature neurons. Organoids made from patient-derived cells showed premature neuronal differentiation in a model of microcephaly, which the authors suggested may explain the disease. Later single-cell studies tested how consistent these models are. Velasco and colleagues (2019) profiled 166,242 cells from 21 organoids and found that 95% produced nearly identical cell-type profiles, with variability similar to that seen in endogenous brains. Bhaduri and colleagues (2020) reported a less favourable picture: organoids produced broad cell classes but did not reproduce distinct cell subtypes or proper progenitor maturation, and they activated cellular stress pathways that impaired cell-type specification.

The main transplantation result to date is from Revah and colleagues (2022), who grafted human cortical organoids into the somatosensory cortex of newborn athymic rats. The transplanted cells matured into cell types that joined sensory and motivation-related circuits, and optogenetic activation of the organoids could drive reward-seeking behaviour in the rats. Transplanted neurons from organoids derived from people with Timothy syndrome were more complex than in-dish neurons and helped reveal defects linked to the disease. Bhaduri and colleagues also reported that transplanting organoids into mouse cortex alleviated their stress and subtype defects. The 'organoid intelligence' proposal by Smirnova and colleagues (2023) envisages standardised, myelinated, high-density organoids linked to microfluidic perfusion and 3D microelectrode arrays for computing. The authors state that, to their knowledge, no approach using brain organoids as learning systems has been reported.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

Cerebral organoids grown from human pluripotent stem cells formed distinct brain regions, including a cortex-like region that produced mature neurons.

Sources: [1] · Abstract

Organoids made from patient-derived stem cells showed premature neuronal differentiation in a microcephaly model, which the authors suggest may explain the disease.

Sources: [1] · Abstract · medium confidence

In a single-cell study of 166,242 cells from 21 individual organoids, about 95% of organoids produced nearly identical cell-type profiles.

Sources: [2] · Abstract

Cortical organoids produced broad cell classes but did not reproduce distinct cell subtypes or proper progenitor maturation, and they activated cellular stress pathways that impaired cell-type specification.

Sources: [3] · Abstract

Human cortical organoids transplanted into the somatosensory cortex of newborn athymic rats matured into cell types that joined sensory and motivation-related circuits, and optogenetic activation of the organoids could drive reward-seeking behaviour.

Sources: [6] · Abstract

Transplanted neurons derived from people with Timothy syndrome were more complex than in-dish neurons, which helped reveal defects linked to the disease.

Sources: [6] · Abstract · medium confidence

The ISSCR classifies all organoid research as Category 1A, exempt from specialised review, and states there is no biological evidence to support concerns that central nervous system organoids are conscious or can feel pain; the 2025 update revised only the embryo-model sections.

Sources: [4], [5] · Organoids section

Proposed A design or plan that has not yet been built or tested.

Smirnova and colleagues propose standardised, myelinated brain organoids linked to microfluidic perfusion and 3D microelectrode arrays as a basis for biocomputing called organoid intelligence.

Sources: [7] · Main proposals · medium confidence

Speculative An idea or possible use. Not evidence of anything.

To the knowledge of the authors, no approach using brain organoids as learning systems has been reported, so the learning and computing benefits of organoid intelligence are prospective.

Sources: [7] · Stated limitations

Limitations and open problems

  • Most organoids lack blood vessels; the authors of the 2023 organoid intelligence paper state that diffusion reaches only about 300 micrometres, so the core of larger organoids can become necrotic.
  • Organoids do not reproduce regional organisation and circuitry well enough to support higher-order brain function, according to the same 2023 authors.
  • Organoids can show cell-stress responses and lack distinct cell subtypes (Bhaduri and colleagues, 2020), and only most, not all, organoids are reproducible (Velasco and colleagues, 2019).
  • No approach using brain organoids as learning systems has been reported, to the knowledge of the authors, so 'organoid intelligence' remains a proposal rather than a demonstrated computing method (Smirnova and colleagues, 2023).
  • The rat transplantation evidence comes from one published study in newborn athymic rats, and no replication is cited in the sources reviewed here. Its findings show circuit integration, not cognition or memory.
  • Whether organoids could become conscious or feel pain is unresolved. The ISSCR says there is no biological evidence to support such concerns for central nervous system organoids, but it asks for continued review as the science advances (ISSCR, 2021).

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Organoid-based biocomputing that stores and processes information, linking standardised organoids to microelectrode arrays and AI analysis (Smirnova and colleagues, 2023 proposal).
  • Patient-specific brain organoids used to test drug responses in neurodevelopmental and neurodegenerative conditions.
  • Hybrid systems that connect brain organoids to sensory organoids, such as retinal organoids (Smirnova and colleagues, 2023 proposal).

Timeline

  1. 28 Aug 2013Lancaster and colleagues report cerebral organoids that form distinct brain regions and a patient-derived microcephaly model in Nature. Sources: [1]
  2. 5 Jun 2019Velasco and colleagues report that 95% of 21 individual dorsal forebrain organoids produce nearly identical cell-type profiles in Nature. Sources: [2]
  3. 29 Jan 2020Bhaduri and colleagues report stress-pathway activation and missing cell subtypes in cortical organoids in Nature. Sources: [3]
  4. 27 May 2021ISSCR 2021 update to its stem cell guidelines places all organoid research in Category 1A, exempt from specialised review. Sources: [4]
  5. 12 Oct 2022Revah and colleagues report human cortical organoids transplanted into newborn rats that integrate into sensory circuits and support optogenetically driven reward-seeking in Nature. Sources: [6]
  6. 28 Feb 2023Smirnova, Hartung and colleagues publish 'Organoid intelligence' in Frontiers in Science, proposing brain organoids for biocomputing. Sources: [7]

Futures this could help bring about

AI illustration
How far away?

Replacing animal testing with lab-grown human tissue

Pilots · 4 of 7 steps done

Glossary

Organoid
A small three-dimensional tissue grown in a dish from stem cells that organises into structures resembling part of an organ.
Pluripotent stem cell
A cell that can develop into most cell types of the body, such as induced pluripotent stem cells made from adult cells.
Optogenetics
A method that uses light-sensitive proteins to switch specific neurons on or off.
Avascular
Without blood vessels, so oxygen and nutrients must diffuse into the tissue from outside.

Sources

  1. peer reviewed paper
    Cerebral organoids model human brain development and microcephaly
    MA Lancaster, M Renner, CA Martin. Nature, 28 Aug 2013. DOI: 10.1038/nature12517. Accessed 21 Oct 2026.
  2. peer reviewed paper
    Individual brain organoids reproducibly form cell diversity of the human cerebral cortex
    S Velasco, AJ Kedaigle, SK Simmons et al.. Nature, 5 Jun 2019. DOI: 10.1038/s41586-019-1289-x. Accessed 21 Oct 2026.
  3. peer reviewed paper
    Cell stress in cortical organoids impairs molecular subtype specification
    A Bhaduri, MG Andrews, W Mancia Leon. Nature, 29 Jan 2020. DOI: 10.1038/s41586-020-1962-0. Accessed 21 Oct 2026.
  4. standard
    ISSCR Guidelines for Stem Cell Research and Clinical Translation: The 2021 update
    R Lovell-Badge, E Anthony, RA Barker. Stem Cell Reports, 27 May 2021. DOI: 10.1016/j.stemcr.2021.05.012. Accessed 21 Oct 2026.
  5. standard
    Guidelines for Stem Cell Research and Clinical Translation (ISSCR, August 2025 update, version 1.2)
    International Society for Stem Cell Research, Aug 2025. Accessed 21 Oct 2026.
  6. peer reviewed paper
    Maturation and circuit integration of transplanted human cortical organoids
    O Revah, F Gore, KW Kelley et al.. Nature, 12 Oct 2022. DOI: 10.1038/s41586-022-05277-w. Accessed 21 Oct 2026.
  7. review article
    Organoid intelligence (OI): the new frontier in biocomputing and intelligence-in-a-dish
    Lena Smirnova, Thomas Hartung. Frontiers in Science, 28 Feb 2023. DOI: 10.3389/fsci.2023.1017235. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.

Changes on 21 Oct 2026
Published on owner instruction (content loop iteration 16)f4c33e6
Sources and claims re-checked against originalsfbb434c
Initial profile drafted from primary sources7e66249