Comparing the brain of a mathematician with that of a sommelier, we find remarkable similarities. In both cases, the cellular density of white and gray matter in designated areas increases. Whether it’s sniffing Syrah or performing calculus, the acquisition of expertise makes parts of the brain thicker. In mathematicians, for example, one of the most prominent changes in the density of gray matter is found in the superior frontal gyrus, an area also linked with the coordination of self-awareness and, most intriguing, laughter. In comparison, changes in sommeliers’ brain volume were found in the right insula and entorhinal cortex, areas that are notably involved in memory processing. Such changes in neural density give those areas enhanced cortical connectivity and signaling speed, as the synaptic connections by which neurons communicate become more tightly packed. A consequence of increased neural density is that dedicated specialized areas of the brain better integrate and orchestrate otherwise widespread neural activity. Expertise of any kind results in a more sophisticated communication architecture of the brain.