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{{Theory Example

|Title=Counting Cells

<blockquote> When it comes to acquiring data about such minute objects as molecules or living cells, the unaided human eye is virtually useless. This proposition yields, among other things, an abstract requirement that, when counting the number of cells, the resulting value is acceptable only if it is obtained with an “aided” eye. This abstract requirement has been implemented in a variety of different ways. First, there is the counting chamber method where the cells are placed in a counting chamber – a microscope slide with a special sink – and the number of cells is counted manually under a microscope. There is also the plating method where the cells are distributed on a plate with a growth medium and each cell gives rise to a single colony. The number of cells is then deduced from the number of colonies. In addition, there is the flow cytometry method where the cells are hit by a laser beam one by one and the number of cells is counted by means of detecting the light reflected by the cells. Finally, there is the spectrophotometry method where the number of cells is obtained by means of measuring the turbidity in a spectrophotometer.[[CiteRef::Barseghyan (2015)|pp. 151-152]]</blockquote>