Cuvettes are used in fluorometry and transmission spectrophotometry to contain the samples. Use of the term 'cells' for cuvettes is discouraged, to avoid confusion with 'living cells'. Traditionally cuvettes have a square cross-section (10 x 10 mm). For many applications they are made of transparent plastic. Glass cells are used where samples may contain plastic solvents, and for some applications requiring measurements below 300 nm, quartz glass or high purity fused silica cuvettes may be necessary.