Microplates: what are they and how do they work?

Microplates and the readers required to measure the results have been in use within scientific and pharmaceutical labs for decades, but few people outside the industry have even heard the terms. So what exactly are microplates and microplate readers and how do they work?

What are microplates?

Microplates, also known as microwell plates or multiwells, are flat plates with multiple deep indentations, or wells, that function effectively like groups mini test tubes. They have been used within the scientific industries for decades, but over the last quarter century have become more standardised thanks to interventions by the Society for Biomolecular Screening (SBS), which has led to improved competition, lower prices, and more ingenuity.

The wells are arranged in standard 2:3 rectangular matrixes, and vary in size from small sample six well plates to 3456 sample wells. The wells themselves vary in size, with some so small they can only hold tens of nanolitres of liquids or powders, whilst others have a volume in the millilitre range.

The exact materials used to create the microplates varies depending on the experiments they are designed for, and are created via injection-moulding techniques. Most are manufactured from a polystyrene base, which can be coloured white (by adding titanium dioxide) when used in experiments measuring optical absorbance or luminescence, or white (by adding carbon) in experiments measuring fluorescent biological assays. Meanwhile, others can be made from polypropylene, polycarbonate, cyclo-olefins, glass or quartz.

What are microplate readers?

Microplate readers, also commonly known as microplate photometers or simply plate readers, are scientific instruments used in labs to detect and measure chemical, biological or physical reactions within the wells of a microplate.

Manually measuring the reactions from a single plate with 3456 samples could take weeks of work for a lab technician, but a microplate reader, such as those produced by BMG labtech, can measure and record the results from each of these wells within minutes or even just seconds. Such quick results dramatically improves the efficiencies within labs and frees researchers to dedicate their time to data analysis and the generation of actionable insights rom the results.

The standardisation of microplates and the rapid results they offer has led to their use becoming commonplace across a variety of sectors from biochemical and pharmaceutical research to the food and cosmetics industries.

How do microplate readers work?

Microplate readers detect absorbance, fluorescence intensity, luminescence, time-resolved fluorescence, and fluorescence polarization events of microplates samples.


For absorbance to be measured, a light source with a specific wavelength is used to illuminate the sample from one side and a light detector on the other side measures how much of the light is transmitted through the sample.

Fluorescence intensity

To measure fluorescence intensity a specific wavelength of light is used to excite the sample, causing it to illuminate (fluoresce), and a second optical system collects the light emitted. This light is separated from the original excitation light using a filter and the remaining signal is measured with a photomultiplier tube (PMT).

Fluorescence polarization

Fluorescence polarization is measured in a very similar way to fluorescence intensity, but with the addition of polarizing filters on the light path.

Time-resolved fluorescence

Time-resolved fluorescence is measured in a similar way to fluorescence intensity but the light emitted by the sample is measured while excitation by the original light source is taking place with the aid of lanthanides, rather than immediately afterwards.


Luminescence is the result of a chemical or biochemical reaction and therefore requires no external light source. As such, luminescence will generally be measured optically with a PMT detector within a light-tight reading chamber.