Abstract: An assembly for optical preconditioning of an optically activatable biological sample comprising of cells suspended in a liquid, with a reservoir which stores the sample from which the sample are conveyed a conveying unit through a hollow channel sequentially one after the other. An illumination unit illuminates the cells contained in the sample which flow through the hollow channel at a flow rate that can be specified by the conveying unit as set by a controllable illumination intensity and illumination period and at least one of a cell analysis and sorting device in fluid communication downstream of the hollow channel.