1. Apparatus for monitoring a system in which a fluid flows, and which is characterized by a change in the system with time in space comprising: A. a monitor for monitoring a preselected area or volume of a system in which a fluid flows and which is characterized by a change in the system with time in space to collect data at a plurality of preselected time points correlated to a system event; B. said collected data being in the form of signal intensities indicative of a system parameter to be measured that varies with time as a function of system wash-in behavior and system wash-out behavior; C. a processor for processing said collected data of signal intensities by a. dividing the preselected area or volume of the system into a grid; b. selecting three of the preselected time points on the basis of a predetermined criteria such that a first time point is before the monitoring step, a second time point is temporally after the first time point on the basis of the predetermined criteria, and the third time point is temporally after the second time point on the basis of the predetermined criteria; c. determining for each grid location at said selected time points values of said signal intensity; d. colorizing and producing an output of each grid point with respect to one of (i) color intensity on the basis of a plurality of distinct wash-in behaviors and an intensity function, and (ii) color hue of one of a plurality of colors on the basis of a plurality of distinct wash-out behaviors and a color function, determined from the signal intensities at the said grid point for the said selected preselected time points; D. a generator for generating from the outputs of said colorized grid points one of (i) a color intensity coded map, and (ii) a color hue coded map representative of said system parameter to be measured in two or three dimensions.