Memoize is a package for externalization of graphics and memoization of compilation results in general, allowing the author to reuse the results of compilation-intensive code. Memoize (i) induces very little overhead, as all externalized graphics is produced in a single compilation. It features (ii) automatic recompilation upon the change of code or user-adjustable context, and (iii) automatic externalization of TikZ pictures and Forest trees, easily extensible to other commands and environments. Furthermore, Memoize (iv) supports cross-referencing, TikZ overlays and Beamer, (v) works with all major engines and formats, and (vi) is adaptable to any workflow.