Acsets are a novel infrastructure for handling data of different shapes, based on category theory and implemented in Catlab.jl. Acsets generalize both graphs and dataframes, and allow a much more general approach to data manipulation than was previously available. We will discuss both the mathematics of acsets and some of the metaprogramming techniques we used to implement them in Julia. Finally, we will give examples of how acsets have been key in developing many projects in AlgebraicJulia.