Despite the global prevalence of children learning more than one language, childhood multilingualism studies has taken off in earnest only since the late 1980s, with the vast majority of that work examining children who have acquired two languages from birth, or simultaneous bilinguals. Overall, global measures of language development (e.g., developmental milestones, total language scores) typically do not differ between bilinguals and monolinguals. However, the development of each language of the multilingual is closely tied to exposure to the specific language. Children learning a second language later in toddlerhood, or sequential bilinguals, are not as well researched, but their development and the factors associated with better second‐language acquisition are also summarized. Finally, outside of language, there is some evidence that the cognitive control associated with navigating multiple languages can lead to bilingual advantages in general cognitive control, even in infancy.