Scientific computing has become of more and more importance for modern research. Especially the finite element method has grown to become one of the most majorly used methods in this field. Writing simulation software on your own, that is oftentimes only designed for just one particular task, is very time consuming and likely prone to errors, since all the basic data infrastructure and linear algebra has to be supplied from scratch. In this talk, we will present the open-source software library `deal.II' that supports the creation of finite element codes by supplying all the tools and infrastructure necessary to build specialized simulation software, involving parallelization and adaptive methods.