N6-methyl-adenosine (m⁶A) is the most abundant modification in mammalian mRNA and long non-coding RNA. First discovered in the 1970s, m⁶A modification has been proposed to function in mRNA splicing, export, stability, and immune tolerance. Interest and excitement in m⁶A modification has recently been revived based on the discovery of a mammalian enzyme that removes m⁶A and the application of deep sequencing to localize modification sites. The m⁶A demethylase fat mass and obesity associated protein (FTO) controls cellular energy homeostasis and is the first enzyme discovered that reverses an RNA modification. m⁶A Sequencing demonstrates cell-type- and cell-state-dependent m⁶A patterns, indicating that m⁶A modifications are highly regulated. This review describes the current knowledge of mammalian m⁶A modifications and future perspectives on how to push the field forward.