It’s an awesome open-source package to solve differential equations using the finite element method. I was lucky enough to get accepted in the google summer of code to work on the mesh processing pipeline in the new version of FEniCS, tag named FEniCS-X. You can find more about my experience here. I was also interview by numfocus during GSoC and you can find that here. The output of the program is mentioned on the google-summer-of-code website here.