This article summarizes the results of a case study on the development of three languages in a child exposed to Tagalog, Spanish, and English from birth. The paper brings together findings from phonology, lexicon, word order, and language choice, providing a detailed picture of the emergence of the four components of three languages in infancy. The paper further explores the possible mechanisms upon which multiple language representations could be built, and then, it examines what characteristics of the environment and of the individual child might lead to the development and active use of three languages in infancy. The results suggest that the build-up of multiple language systems might follow naturally from trilingual exposure; yet, factors such as quantity and quality of language exposure, linguistic relatedness among languages, the child's personality, and the nature of the social context may dramatically influence trilingual competence in infancy and early childhood.