Studying the cellular activity of the brain requires good spatial and temporal resolutions and most importantly optical sectioning, but current imaging systems can become quite expensive, need special care or do not have all the required properties. In addition, the FOV is reduced to reach reasonable acquisition speed, which prevents whole-brain imaging. Here, we present HiLo microscopy to acquire volumetric activity of the zebrafish brain in vivo. This project focuses on improving our knowledge of the brain-gut-microbiota axis in a living organism.