This book presents the latest research on multisensory brain function. Namely, the mechanisms by which the brain processes and integrates information from multiple sensory modalities. Its contents cover a broad range of topics, including optimal integration, cross-modal interactions, calibration, and causal inference - with an emphasis on their neuronal underpinnings. By bringing together efforts from different laboratories around the world we aim to collaboratively shed light on these fundamental brain processes, that underlie perception, cognition, and behavior in a complex multisensory world, and to spur innovation of brain-inspired technologies