Light stimulations and optical recordings of neuronal activity are two promising approaches for investigat-ing the molecular mechanisms at the basis of neuronal physiology. In particular, flash photolysis of caged compounds [1] offers the unique advantage of allow-ing to quickly change the concentration of either in-tracellular or extracellular bioactive molecules, such as neurotransmitters or second messengers, for the stimulation or modulation of neuronal activity. More-over optical recordings of neuronal activity by Volt-age-Sensitive Dyes (VSDs) [2] allow to follow changes of neuronal membrane potential with high-spatial resolution. This enables the study of the sub-cellular responses and that of the entire network at the same time. In the last decade, studies on neuronal physiology and plasticity have provided a detailed picture of the mo-lecular mechanisms underlying the modulation of neuronal activity; on the other hand, the molecular mechanisms which control the network properties re-main poorly understood, and represent a new frontier in neuroscience. Two different approaches can be fol-lowed for the study of neuronal functions: a large-scale approach aiming at u nderstanding the activity of many neurons interacting in a complex network and a micro-scale approach aiming at providing detailed be-havioural models of the molecular systems which ac-tively contribute to the generation and modulation of the neuronal activity. A new breakthrough in neuroscience would be the possibility to stimulate and modulate a single neuron, or selected parts thereof, and study its influence over the functioning of the entire network. In this manner, the micro-scale meets the large-scale approach, allowing the understanding of how the mechanisms that influence the physiology of single neuronal units are able to alter the behavi our of the entire network. At present, experiments are carried out by electrical stimulations and recordings using intracellular or extracellular electrodes as well as MicroElectrode Array devices. These systems have yielded important results but show some limits, e.g. in terms of mechanical damage of the cell (intracellular electrodes) and poor spatial resolution both in stimulation and recording (MEA). In addition to traditional electrophysiology tech-niques, optical methods for stimulating (using Caged Compounds) and recording (using Voltage-Sensitive fluorescent Dyes) neuronal activity have been used separately for a long time. Typically light stimulations are combined with electrical recordings, whereas opti-cal recordings with el ectrical stimulations. First experiments of optical stimulation and imaging were done with a microscope -based set-up (Figure 1). Figure 1: This figure represents the set-up for a total optical analysis of neuronal networks. Three pathways were sown: that of light stimulation (Red line), that of MEA recordings (Green line) and that of optical re-cordings (Black line). In this set-up MEA recordings were used as validation of the optical stimulations. Figure 2 (Top panel) shows a neuronal spike evoked with a 100msec UV stimulus for activating the caged-glutamate (MNI-caged-L-glutamate, Tocris Bioscience, Bristol, UK) used in a 100uM concentration. Figure 2 (Bottom panel) shows the Ca