What is a microplate?
The plain-language answer: what it is, what it is for, and how to tell one plate from another.
A microplate (also called a microtiter plate or a multiwell plate) is a flat, usually rectangular plastic plate holding a grid of small, separate wells. Each well works like a miniature test tube, holding a small volume of liquid, so one plate carries dozens or hundreds of independent samples, reactions, or cell cultures side by side.
Every microplate shares the same standard footprint, 127.76 mm by 85.48 mm under the ANSI/SLAS standards, which is why the same plate moves between a pipette or liquid handler, an incubator, a shaker, and a plate reader without being repacked. The format is older than the instruments: Gyula Takatsy machined the first plates in 1951, during an influenza epidemic, to replace rows of test tubes.
The problem a microplate solves
Scale. Many experiments are not one measurement but hundreds: the same assay on many samples, many concentrations of one compound, or many replicates of one condition. Run in individual tubes, that is slow, error-prone, and thirsty for reagent. A plate puts everything in one organized, addressed grid, uses microliters instead of milliliters per point, and lets one instrument process the whole set in a single pass.
Who uses microplates, and for what
- Immunoassays and enzyme assays: measuring how much of a protein, antibody, or enzyme activity is present, by color, fluorescence, or light output in each well.
- Cell culture and cell-based assays: growing a small culture in each well and testing how cells respond to different treatments, many conditions at once.
- Screening: testing large collections of compounds or samples against a target, where throughput is the point.
- Molecular biology: setting up PCR and sequencing reactions, preparing libraries, and storing nucleic acid samples in an addressed layout.
- Sample storage: holding aliquots in deep well plates, where each position corresponds to a known sample, at bench or freezer temperatures.
- Teaching laboratories: a plate lets many students run parallel small-scale experiments at modest reagent cost.
The five choices that define a plate
Number of wells. Plates run from 6 wells to 1,536. The 96 well format is the workhorse: 8 rows (lettered A to H) by 12 columns (numbered 1 to 12), so every well has an address, such as B7. Fewer, larger wells suit cell culture; more, smaller wells (384, 1,536) raise throughput and cut reagent use, but demand precise liquid handling, usually automation.
Well shape. Flat bottoms suit optical readings and adherent cell growth. Round (U) bottoms suit mixing and suspension work and let pelleted material gather loosely. V bottoms concentrate small volumes and pellets at a point, which helps when every microliter has to be recovered.
Color. Clear plates pass light for absorbance readings. White plates reflect emitted light back to the detector and suit luminescence. Black plates absorb stray light and suit fluorescence, where background and cross-talk between wells must stay low. Black plates with clear bottoms combine clean readings with a view of the cells from below.
Surface. Plain polystyrene is somewhat hydrophobic. Plates are also sold treated to bind protein strongly (assay and ELISA plates), treated so cells attach (tissue culture plates), or made to resist binding, for work where the sample sticking to the plastic is the failure mode. Some polypropylene plates carry a thin glass coating inside the wells for long compound storage.
Material. Most plates are polystyrene: clear, rigid, and inexpensive. Polypropylene is opaque, tolerates wider temperature swings and a broader range of solvents, and is the default for storage and PCR. Match the plastic to the chemistry and the temperature, not just the budget.
Microplate vs the things it gets confused with
Vs a test tube or sample tube. A tube holds one sample and is handled one at a time. A plate holds many samples in a fixed layout and is handled as one unit, which is what makes automation and plate instruments practical.
Vs a petri dish. A dish offers one open surface, usually for growing colonies on a solid medium. A microplate offers many separated liquid compartments, so conditions can be compared directly, in parallel.
Vs a plate reader. The plate is the consumable that holds the samples; the reader is the instrument that measures them. They are bought separately, and the reader has to match the plate format and optical type in use.
Vs a deep well plate. A deep well plate is a microplate, same footprint, with much deeper wells holding up to about 2.2 mL each. It is used to store and prepare samples rather than to read them optically. The deep well plate guide covers that family in full.
Handling pitfalls that actually bite
- Orientation errors. Results attach to well addresses, so a rotated or flipped plate quietly attaches the right result to the wrong sample. Plates have a notched corner at A1 for orientation; label the plate itself, not only the lid, because lids get swapped.
- Bubbles and uneven volumes. A bubble or a short fill distorts an optical reading. Careful pipetting, and dispensers where volume justifies them, keep wells even.
- Cross-contamination. Wells sit millimeters apart, so splashes, drips, and reused tips carry material between them. Lids, seals, and disciplined tip changes are the usual defenses.
- Evaporation and condensation. Small volumes shrink noticeably over long incubations, edge wells first, and condensate forms on lids. Sealing films, humidified incubators, and breathable seals for culture are the standard remedies.
- Static and dust. Fresh plastic carries a static charge that attracts dust and makes small droplets misbehave, worst at the smallest volumes.
None of these is exotic. They are why experienced users treat the plate as part of the experimental design, not as a neutral container.
The short version
A microplate is a standardized plate of small wells that lets many samples be handled, incubated, and measured together. The choices that matter are the well count, the well shape, the color for the readout, the surface treatment, and the plastic. Getting those right for the assay, and confirming the plate fits the reader and any automation, matters more than the price per plate.
Related guides
Common questions
What is a microplate used for?
Running many small samples, reactions, or cell cultures in parallel. Common uses are immunoassays, enzyme assays, cell-based tests, compound screening, PCR and sequencing setup, and organized sample storage.
Is a microplate the same as a 96 well plate?
A 96 well plate is the most common kind of microplate, not the whole category. Microplates run from 6 large wells to 1,536 small ones; 96 is the workhorse format in the middle.
Why do microplates come in different colors?
Color controls how light behaves in the reader. Clear plates suit absorbance, white plates suit luminescence because they reflect emitted light to the detector, and black plates suit fluorescence because they absorb stray light and cut cross-talk between wells.
What is the difference between a microplate and a plate reader?
The microplate holds the samples; the plate reader is the instrument that measures light, color, or fluorescence from each well. You need both, and they must be compatible in format and optical type.
Why do the outer wells sometimes give different results?
Edge wells lose liquid to evaporation faster and sit at slightly different temperatures than interior wells, a pattern called the edge effect. Labs seal plates, fill unused edge wells with liquid, or randomize positions to limit it. The knowledge base page on this site covers the causes and fixes in full.
Can a microplate be reused?
Most are designed as single-use consumables, and reuse risks contamination and inconsistent results. Polypropylene plates can be autoclaved where a maker allows it; polystyrene cannot. For rough preparation work some labs wash and reuse, but quantitative assays assume a fresh plate.