A method for performing photo-modification of a biological sample, the method comprising: (a) irradiating the sample; (b) detecting one or more signals based on the irradiated sample; (c) using one or more processor means to analyze the detected signals and determine one or more irradiation parameters, and, (d) returning to (a) conditioned on the irradiation parameters. Thus modifications may be determined and executed interactively as an experiment progresses, and therefore directed towards specific structures and/or events identified as of particular interest in the course of the experiment.