The chapter shows that bilingual language use strengthens general cognitive control networks, yielding behavioral advantages in cognitive control and changes to the neural system. A major focus of bilingual brain research is to determine if the degree of control necessary to manage languages differs when a bilingual is in a single-language context or a mixed-language context. It is important to realize that individual differences in bilinguals influence the organization of the bilingual brain. Large effects in the bilingual brain have been attributed to proficiency, the linguistic competence and fluency in each language. Language systems and other cognitive control systems work together to ensure words are spoken in the appropriate language. A model of the language networks in the brain has been proposed based on compilation of hundreds of neuroimaging studies. Bilinguals are able to produce and/or comprehend more than one language and demonstrate better understanding of the formal properties of language than monolinguals.