The microplate reader is a multimodal instrument that allows for a variety of experiments to be performed and measured simultaneously. Microplate readers can make absorbance, fluorescence and luminescence measurements. Multiwell plates are integral to the microplate reader and allow for many experiments to be performed at once. Regardless of the assay type, experiments on the plate reader utilize a standard curve to determine the experimental values. This curve uses samples of known concentration to generate a line of best fit or standard curve. Experimental values are then extrapolated to the curve or are calculated using the equation from the linear regression. Besides standards and samples being run on the multiwall plate, the blank along with positive and negative controls are also used in the assay to ensure it is working correctly. Multiplate readers are used to quantify protein, gene expression and various metabolic processes such as reactive oxygen species and calcium flux.