Explainer
What Is a Well Plate?
A well plate, also called a microplate or microtiter plate, is a flat tray of small wells that lets a lab run many samples at once. Here is what they are, the standard formats, and how they are used.
Quick answer
A well plate, also called a microplate, microtiter plate or microwell plate, is a flat, rectangular tray with a grid of small wells, each acting as a miniature test tube. It lets a lab run many samples in parallel under identical conditions, read by standard instruments. Common formats are 6, 12, 24, 48, 96 and 384 wells; the 96-well plate is the most widely used.
- A well plate is a standardized tray of small wells for parallel samples.
- Synonyms: microplate, microtiter plate, microwell plate, multiwell plate.
- Standard formats: 6, 12, 24, 48, 96 and 384 wells on one SBS/ANSI footprint.
- Used for ELISA, qPCR, optical assays, cell culture and screening.
Definition
A well plate is a rigid, rectangular tray moulded with a regular grid of small depressions called wells. Each well holds a small volume of liquid, from a few microlitres to a few millilitres, and behaves like an independent miniature test tube. Because every well on a plate is handled, incubated and read together, the format is ideal for comparing many conditions under identical circumstances.
The terms microplate, microtiter plate and microwell plate all mean the same thing. Plates share a standardized outer footprint so they fit the readers, washers and liquid handlers found in any lab.
Common well plate formats
Standard plates differ mainly in how many wells share the same footprint:
| Format | Layout | Working volume | Typical use |
|---|---|---|---|
| 6-well | 2 × 3 | 1.9–2.5 mL | Cell expansion |
| 12-well | 3 × 4 | 1.0–2.0 mL | Cell culture |
| 24-well | 4 × 6 | 0.5–1.0 mL | Primary culture |
| 48-well | 6 × 8 | 0.2–0.5 mL | Optimization |
| 96-well | 8 × 12 | 100–200 µL | ELISA |
| 384-well | 16 × 24 | 20–50 µL | High-throughput screening |
Parts of a well plate
Most of a plate exists to make the wells easy to handle, read and automate. The vocabulary is worth knowing because catalogue listings and instrument manuals use it:
- Wells. The moulded cavities that hold sample. Their number, diameter and depth define the format.
- Skirt. The raised outer wall around the wells. It is the surface you write a plate ID on, and on PCR plates its height decides which thermal cyclers accept the plate.
- Flange. The lip at the base that rests on a reader stage or robot deck, and the feature the footprint standard actually controls.
- Lid. A loose cover with moulded rings or ridges that break surface tension, so condensation drips back rather than pooling over the wells.
- A1 marker. Moulded row letters and column numbers, often with a cut or notched corner, which fix the plate’s orientation.
- Barcode panel. A flat area on automation plates for a one or two-dimensional barcode, so a liquid handler can identify the plate without a person reading it.
Well-bottom shapes & materials
Wells come with flat, round (U) or V-shaped bottoms: flat for optical reads and adherent culture, round and V for collecting cells and small pellets. Plates are usually moulded from optically clear polystyrene, or from chemical-resistant polypropylene for storage and PCR. Colour matters too: clear for absorbance, black for fluorescence, white for luminescence.
Flat bottom
Flat optical path for absorbance and imaging, and a surface for adherent cells.
Round / U-bottom
Pools cells and suspensions gently at the centre for washing and pelleting.
V-bottom
Concentrates small volumes to a point so almost all sample can be recovered.
How well plates are used
The parallel, standardized design makes well plates the backbone of the analytical lab: immunoassays like ELISA, nucleic-acid work like qPCR, spectroscopic assays, cell culture and large-scale screening. The 96-well plate is the most common format. See what well plates are used for for detail.
How well plates are made, treated and sterilised
Plates are injection moulded in one piece, normally from optically clear polystyrene for assays and culture, or from polypropylene where solvents, freezing or PCR cycling are involved. Moulding in one piece is what keeps well positions consistent enough for robots to trust.
Culture plates then receive a surface treatment. Plasma or corona discharge turns the naturally water-repellent plastic into a hydrophilic, negatively charged surface that adherent cells can attach to, which is what TC-treated means on a label. Protein coatings such as poly-D-lysine, collagen or fibronectin go further for demanding cells, while ultra-low-attachment coatings do the reverse and keep cells in suspension for spheroid and organoid work.
Sterile plates are packaged first and sterilised in the pack by gamma or electron-beam irradiation, then certified non-pyrogenic and free of detectable DNase, RNase and human DNA. Because polystyrene softens well below autoclave temperature, plates are single use rather than re-sterilised.
Well plates compared with dishes, flasks and tubes
A well plate is not always the right vessel. The choice comes down to how much surface or volume each sample needs, and how many samples must be handled together:
| Vessel | Growth area | Typical volume | Best for |
|---|---|---|---|
| 96-well plate | 0.32 cm² | 100–200 µL | Many parallel assays read by one instrument |
| 6-well plate | 9.6 cm² | 1.9–2.5 mL | Small cultures you still need to harvest |
| 35 mm dish | ≈ 8–9 cm² | 2 mL | One sample, open access for imaging |
| 100 mm dish | ≈ 57 cm² | 10 mL | Bulk growth and colony picking |
| T-25 flask | 25 cm² | 5 mL | Closed, contamination-resistant expansion |
| T-75 flask | 75 cm² | 15 mL | Routine expansion of a cell line |
| 1.5 mL tube | n/a | ≤ 1.5 mL | Single reactions and sample storage |
The pattern is simple. Dishes and flasks give one sample more room, and plates give many samples identical conditions in a footprint every reader, washer and robot already accepts. Compare the formats on the surface area and volume chart.
Where the microplate came from
The format began as a workaround. In 1951, during an influenza epidemic in Hungary, the microbiologist Gyula Takátsy machined a tray of 6 rows by 12 wells out of acrylic so he could run serial dilutions for virus testing far faster than a rack of tubes allowed. He paired it with spiral wire loops that transferred a fixed volume to several wells at once, and published the method in 1955.
Commercial moulded plates followed in the 1960s, and the 8 × 12 arrangement of 96 wells became the default. Instrument makers eventually needed guaranteed dimensions, so the Society for Biomolecular Screening published footprint, height and well-position standards that ANSI approved in 2004. They are maintained today as the ANSI/SLAS microplate standards, and they are the reason a plate from one supplier fits a reader from another.
Frequently asked questions
What is a well plate?
A well plate, or microplate, is a flat, rectangular tray containing a grid of small wells, each acting as a tiny test tube. It lets a scientist run many samples or reactions in parallel under identical conditions, and is read by standard laboratory instruments.
What is a well plate used for in chemistry and biology?
Well plates are used for assays such as ELISA, qPCR, absorbance, fluorescence and luminescence measurements, cell culture, and high-throughput screening: anywhere many small, parallel samples need consistent handling.
What are the common well plate sizes?
The standard formats are 6, 12, 24, 48, 96 and 384-well plates. All share the same outer footprint; higher-well-count plates simply pack more, smaller wells into it.
Why are they called microtiter or microwell plates?
'Microtiter plate' comes from micro-scale titration, an early use. 'Microplate' and 'microwell plate' are synonyms for the same standardized labware.
What material are well plates made of?
Polystyrene is the default, because it moulds cleanly, stays optically clear and takes the surface treatment that adherent cells need. Plates meant for freezing, solvents or thermal cycling are moulded in polypropylene instead. Where a reading falls in the ultraviolet range, ordinary plastic absorbs too much light, so UV-grade plates or quartz-bottom plates are used.
What is the difference between flat, round and V-bottom wells?
Flat-bottom wells give a uniform optical path for absorbance reads and a surface for adherent cells; round (U) bottoms gently collect cells and suspensions; V-bottoms concentrate small pellets so almost all sample can be recovered. Bottom shape is chosen to match the assay.
How big is a well plate?
Every standard format occupies the same rectangle, roughly the size of a postcard, and stands about as tall as a finger is wide. Height varies with plate type, from shallow assay plates to deep-well blocks. Only the wells inside change between formats, which is what lets one reader or robot accept all of them.
Are well plates sterile?
Plates sold for cell culture are sterile. They are moulded, packaged and then sterilised by gamma or electron-beam irradiation, and suppliers usually certify them as non-pyrogenic and free of detectable DNase, RNase and human DNA. Plates sold for general laboratory use, such as basic assay or storage plates, are often supplied non-sterile.
Can you autoclave or reuse a well plate?
No. Polystyrene plates soften well below the 121 °C of a standard autoclave cycle, so they warp and are treated as single use. Reusing a plate also risks carry-over between experiments and damages the surface treatment that adherent cells rely on. Polypropylene storage plates tolerate freezing and solvents better, but they are still not meant for re-sterilising.
What is the difference between a well plate and a Petri dish?
A Petri dish is one open culture surface, usually 35 to 100 mm across, handled on its own. A well plate holds many separate wells in one standardised tray, so dozens of conditions are grown, treated and read together. A 35 mm dish and a single 6-well well offer a similar growth area, but the plate keeps six of them in a footprint that fits a reader or robot.
What does TC-treated mean on a cell culture plate?
TC-treated, or tissue-culture treated, means the moulded plastic has been modified by plasma or corona discharge so the surface becomes hydrophilic and negatively charged. Adherent cells attach and spread on that surface, where they would struggle on untreated polystyrene. Untreated plates suit suspension cells, and ultra-low-attachment coatings deliberately prevent attachment for spheroid work.