Cell Painting Explained: A Complete UK Guide for 2026

What Is Cell Painting?

Cell Painting is a high-content, image-based assay that captures the morphology of cells using a standard set of six fluorescent dyes. Each dye stains a different cellular compartment, and together they generate a multi-channel image that can be analysed to extract thousands of morphological features. The result is a rich phenotypic fingerprint of a cell population under a particular condition, treatment or genetic perturbation.

The technique was developed by researchers at the Broad Institute and has become one of the most widely used image-based profiling tools in drug discovery. Rather than measuring one specific molecular target, Cell Painting asks a broader question: what does the cell look like when treated with this compound or gene modification? That morphological signature can be compared against a reference database to predict mechanism of action, identify off-target effects, or find compounds that produce a similar phenotype.

The assay is deliberately simple in concept: stain cells, image them, extract features, cluster the results. In practice, the microscopy, image analysis and data interpretation all need to be robust and reproducible. This guide explains how Cell Painting works, which microscopes can run it, and what UK labs should consider when building a Cell Painting workflow.

For microscope comparisons and UK pricing, see our dedicated Cell Painting microscopy guide or the Cell Painting section on the Plankton & Zoom homepage.

The Six Stains and What They Reveal

The classic Cell Painting assay uses six fluorescent dyes in five channels. Each dye highlights a specific cellular structure, so the combined image captures information about nucleus, cytoplasm, nucleoli, endoplasmic reticulum, Golgi, plasma membrane, mitochondria and actin cytoskeleton.

From these six stains, image analysis software typically extracts between 1,500 and 5,000 features per cell. Features include intensity, texture, shape, size, granularity and correlation between channels. When multiplied across thousands of cells per well and many wells per plate, the dataset becomes large enough to train machine learning models or to cluster compounds by phenotypic similarity.

How Cell Painting Is Used in Drug Discovery

1. Mechanism-of-Action Prediction

The most common application is predicting how an unknown compound works. A drug that produces a morphological signature similar to a known kinase inhibitor is probably also affecting kinases. This approach has been used in large public datasets such as the JUMP Cell Painting Consortium, where thousands of compounds and genetic perturbations have been profiled.

2. Target and Pathway Deconvolution

When a phenotypic screen identifies a hit, the next challenge is finding its molecular target. Cell Painting profiles can suggest pathways by comparing the hit against profiles from genetic knockouts or known pathway modulators. The Broad Institute's CellProfiler-based pipelines and the JUMP dataset make this accessible to labs that do not have their own large reference library.

3. Toxicity and Safety Profiling

Cell Painting picks up subtle toxicity signatures early. Changes in mitochondrial morphology, ER stress, nuclear condensation or actin reorganisation can all indicate off-target effects. Comparing a lead compound against a toxicant reference profile helps flag safety liabilities before expensive animal studies.

4. Disease Model Characterisation

Patient-derived cells, iPSC models and CRISPR-edited disease models often show subtle morphological changes. Cell Painting can quantify those differences and measure whether a candidate drug normalises the phenotype. This is particularly valuable in neurodegeneration, rare disease and cancer biology where animal models are limited.

5. Compound Library Clustering and Hit Expansion

Large compound libraries can be screened at low cost by imaging a single concentration and clustering hits by phenotype. Chemically diverse compounds that produce similar morphological profiles may share a target or pathway, expanding the chemical space around a promising series.

Microscopes and High-Content Systems That Can Run Cell Painting

Cell Painting does not require a super-resolution microscope. It needs reliable multi-channel fluorescence imaging across many fields of view and many wells, with minimal photobleaching and consistent illumination. The most important practical factors are:

• Five fluorescence channels: Blue, green, yellow, red and far-red to separate the six dyes.
• Stable illumination: LED or solid-state light sources give better day-to-day reproducibility than ageing mercury lamps.
• Automated stage and autofocus: Essential for imaging multiple wells with consistent field selection.
• Sensitive camera: A good CMOS or sCMOS detector with linear response and low read noise.
• Compatible objectives: 10x or 20x plan-fluorite objectives are standard; 20x captures more sub-cellular detail.
• Software and data export: Must export individual channel TIFFs or compatible formats for CellProfiler or other analysis pipelines.

CellInsight CX7 Pro / CX7 LED Pro

The Thermo Fisher CellInsight CX7 Pro High Content Screening Platform is one of the most frequently recommended systems for Cell Painting. It is a true high-content screening instrument, designed for 96- and 384-well plates with automated liquid handling integration, environmental control and plate-stack loading.

Key reasons the CX7 fits Cell Painting well:

• Seven-channel fluorescence: More than enough for the standard Cell Painting panel plus an extra channel for a target-specific marker.
• Confocal and widefield options: The Pro model can use a confocal scanning unit for thicker samples or organoids, while standard widefield mode is faster for 2D monolayers.
• Integrated HCS Studio software: Image acquisition, segmentation and feature extraction can be handled in one workflow, reducing the need to move data between tools.
• Automation-ready: Optional plate loaders and incubator compatibility make it suitable for true screening rather than one-off imaging.

For UK labs, the CX7 is usually positioned as a high-content screening workhorse rather than a departmental microscope. It makes most sense when Cell Painting will be run repeatedly on multi-well plates, when throughput matters, or when integration with automated liquid handling and analysis pipelines is part of the plan. Indicative UK pricing for a configured CX7 LED Pro typically starts around £150,000–£250,000 depending on confocal, plate loader and software modules.

EVOS M7000

The Thermo EVOS M7000 is a more accessible alternative. It supports up to five fluorescence channels, automated scanning of multi-well plates, Z-stacking, time-lapse imaging and environmental control. While it is not a high-content screening platform in the same class as the CX7, it can absolutely run Cell Painting for smaller libraries, pilot studies and assay development.

UK labs often choose the EVOS M7000 when they need a flexible fluorescence microscope that can do Cell Painting alongside live-cell imaging, confluence tracking and transfection analysis. It is a good bridging instrument before committing to a dedicated HCS platform.

Other Platforms Worth Considering

• Yokogawa CV8000: Confocal high-content system with water-immersion objectives and fast spinning-disk confocal imaging. Excellent for 3D spheroids and organoids as well as 2D Cell Painting.
• Molecular Devices ImageXpress systems: Widely used in pharma; strong software ecosystem for HCS and analysis.
• PerkinElmer Opera Phenix / Operetta: Confocal spinning-disk systems with a long history in Cell Painting literature and large reference datasets.
• Benchtop inverted fluorescence microscopes: For proof-of-concept or very small libraries, a manual or semi-automated inverted fluorescence microscope can run the assay, though throughput and consistency will be lower.

Image Analysis: From Pictures to Profiles

Imaging is only half the workflow. The other half is turning images into numbers. The most common free tool is CellProfiler, an open-source image analysis pipeline developed at the Broad Institute. CellProfiler can segment cells, identify nuclei and cytoplasm, measure intensity and texture features, and export a table of thousands of measurements per image.

For Cell Painting specifically, the Carpenter lab publishes recommended pipelines and module configurations. After feature extraction, the data is typically normalised, feature-selected and clustered. Tools such as pycytominer, Harmony, CellProfiler Analyst and Python libraries like scikit-learn or UMAP are commonly used downstream.

The goal is to produce a feature vector for each well or treatment. Compounds or genetic perturbations with similar vectors are considered phenotypically similar. This can reveal mechanism of action, identify off-target effects, or group hits for follow-up.

Practical Workflow for a UK Lab

1. Cell seeding: Plate cells in 96- or 384-well plates at a consistent density. Allow attachment overnight.
2. Treatment: Add compounds, genetic perturbations or controls. Typical treatment times range from 24 to 48 hours.
3. Fixation: Paraformaldehyde preserves morphology. Some protocols use methanol for improved antibody compatibility.
4. Staining: Apply the six Cell Painting dyes in a fixed order. Washing steps are critical to reduce background.
5. Imaging: Acquire multiple fields per well across all channels. 10x or 20x objective, consistent exposure times.
6. Image analysis: Segment cells and extract features with CellProfiler or HCS software.
7. Profiling: Normalise, feature-select, cluster and compare against reference datasets.

Reproducibility is the biggest practical challenge. Small differences in seeding density, staining time, exposure settings or image analysis parameters can dominate the signal. Running reference compounds, positive controls and batch-effect checks across plates and days is essential.

When Should a UK Lab Buy a Dedicated Cell Painting Platform?

Not every lab needs a CellInsight CX7 or Yokogawa CV8000. The decision should be driven by throughput and workflow maturity.

• Pilot phase: Run Cell Painting on an existing EVOS M7000, inverted fluorescence microscope or core-facility HCS system. Focus on protocol validation and reference profiling.
• Assay development: If the pilot works, consider a mid-range automated platform for medium-throughput screening and larger reference datasets.
• Screening scale: If you plan to screen thousands of compounds or run Cell Painting weekly, a dedicated high-content platform such as the CellInsight CX7 becomes cost-effective.
• Service route: UK CROs and core facilities now offer Cell Painting as a service. This is often the best first step for occasional screens or grant-funded pilot studies.

For current UK microscope prices and buying comparisons, see our UK Microscope Price Guide 2026. For a deeper look at spatial biology technologies that complement Cell Painting, read our Spatial Biology complete guide.