eyeball. 1  Photoreceptors are the cells in the retina that respond to light. Their distinguishing feature is the presence of large amounts of tightly packed membrane that contains the photopigment rhodopsin or a related molecule.
In chemical analysis,  matrix refers to the components of a sample other than the analyte of interest. The matrix can have a considerable effect on the way the analysis is conducted and the quality of the results obtained; such effects are called matrix effects. For example, the ionic strength of the solution can have an effect on the activity coefficients of the analytes.
Full Definition of MATRIX. 1. : something within or from which something else originates, develops, or takes form. 2.. b: the thickened epithelium at the base of a fingernail or toenail from which new nail substance developsâcalled also nail bed, nail matrix. 2. : something (as a surrounding or pervading substance or element) within which something else originates or takes form or develops. 3.