ensure constant temperature during testing. Instrument companies have designed plate readers which can detect specific biological, chemical or physical events in samples stored in these plates. A specialized plate reader has also been developed which can perform quality control of microplate well contents, capable of identifying empty wells, filled wells and precipitate. Manufacture and composition Microplates are manufactured in a variety of materials. The most common is polystyrene, used for most optical detection microplates. It can be coloured white by the addition of titanium dioxide for optical absorbance or luminescence detection or black by the addition of carbon for fluorescent biological assays. Polypropylene is used for the construction of plates subject to wide changes in temperature, such as storage at −80 °C and thermal cycling. It has excellent properties for the long-term storage of novel chemical compounds. Polycarbonate is cheap and easy to mould and has been used for disposable microplates for the polymerase chain reaction (PCR) method of DNA amplification. Cyclo-olefins are now being used to provide microplates which transmit ultraviolet light for use in newly developed assays. There are also microplates constructed from solid pieces of glass and quartz for special applications. The most common manufacturing process is injection molding, using materials such as polystyrene, polypropylene and cyclo-olefin for different temperature and chemical resistance needs. Glass is also a common material, and vacuum forming can be used with many other plastics such as polycarbonate. Composite microplates, filter bottom plates, solid phase extraction (SPE) plates, and even some advanced PCR plate designs use multiple components which are moulded separately and later assembled into a finished product. ELISA plates may now be assembled from twelve separate strips of eight wells, making it easier to only partially use a plate. There are a multitude of formats, with the same footprint but different numbers of wells and heights. The wells are available in different shapes: F-Bottom: flat bottom C-Bottom: bottom with minimal rounded edges V-Bottom: V-shaped bottom U-Bottom: U-shaped bottom There are also deep well microplates sometimes called "blocks", as well as 192 and 768 well plates. The standardization of the microwell plates is made by the Society for Biomolecular Sciences with the ANSI-Standards (ANSI/SBS 1-2004, ANSI/SBS 2-2004, ANSI/SBS 3-2004, ANSI/SBS 4-2004) History The earliest microplate was created in 1951 by a Hungarian, Dr. Gyula Takátsy, who machined six rows of 12 "wells" in Lucite. However, common usage of the microplate began