The brain is one of the most temperature-sensitive organs in the human body, and this feature can be often linked to physiological phenomena and anomalies. Innovative state-of-the-art devices can investigate the neuronal response to temperature transients to assess, for instance, neurodegenerative diseases evolutions. For this purpose, implantable optical stimulation microdevices, or simply optrodes, have been designed by the Research Group of Implantable Microsystems, Pázmány Péter Catholic University, in collaboration with the Hungarian Academy of Sciences. The optrodes are multimodal devices; they simultaneously provide information on thermal and electrophysiological variations, as well as IR infrared light delivery into neural tissue, in a spatially controlled manner.