This study investigates the transcriptional heterogeneity of oligodendrocytes across the juvenile and adult mouse central nervous system (CNS). Single-cell RNA-Seq analysis of 5072 cells from ten regions of the CNS identified twelve distinct populations, ranging from Pdgfra+ oligodendrocyte precursors (OPCs) to mature oligodendrocytes. The initial stages of differentiation were similar across the juvenile CNS, while specific subsets of mature oligodendrocytes were enriched in certain adult brain regions. A second Pdgfra+ population, distinct from OPCs, was found along blood vessels. The study reveals a dynamic differentiation and maturation process of oligodendrocytes, highlighting their transcriptional heterogeneity and suggesting potential roles in active maturation and remyelination processes.This study investigates the transcriptional heterogeneity of oligodendrocytes across the juvenile and adult mouse central nervous system (CNS). Single-cell RNA-Seq analysis of 5072 cells from ten regions of the CNS identified twelve distinct populations, ranging from Pdgfra+ oligodendrocyte precursors (OPCs) to mature oligodendrocytes. The initial stages of differentiation were similar across the juvenile CNS, while specific subsets of mature oligodendrocytes were enriched in certain adult brain regions. A second Pdgfra+ population, distinct from OPCs, was found along blood vessels. The study reveals a dynamic differentiation and maturation process of oligodendrocytes, highlighting their transcriptional heterogeneity and suggesting potential roles in active maturation and remyelination processes.