Abstract: A well reader and actuator (100) for a well array (50) has an array of detectors, each detector for detecting a fluorescence signal from fluorophores in a respective well of the well array and an excitation subsystem for exciting the fluorophores in the wells of the well array. Embodiments of this invention can be used to carry out two important functions in a highly parallel manner: by addressing individual wells in a 32, 96, 384 etc. well array, where each well contains a potential chemical or biological reaction. The two functions are: 1) through thermal, optical or other means and combinations thereof the rate of a chemical or biological reaction is controlled or gated (e.g. colder wells inhibit a reaction, or an enzymatic reaction requires blue light to proceed); and 2) through use of fluorescent species that are sensitive to the target reaction—or reactions—an optical readout of fluorescent intensity and/or lifetime is tracked to monitor the evolution of the reaction.