The functionality of the molecular units or modules is determined mainly by their electronic structure and the surrounding molecular environment. These microscopic properties can be investigated at different levels of theory. Such methods are increasingly exploited to analyze and to predict the structure and functional properties of molecules and materials in many applications. In this course, we will introduce several quantum chemistry methods, with a special focus on the density functional theory (DFT) approach, which are now widely used in the investigation of molecular systems and their properties. We will introduce the basics of the electronic structure methods with the specific application in the photochemistry of molecules used in 3D printing. Moreover, we will demonstrate the applicability of the computational methods in the design of new promising compounds for 3D printing and for the systematic improvement of existing materials. During computer classes, you will learn how to run different types of calculations using standard software packages and to analyze the obtained results. This course provides a solid base to understand the underlying methods and is adapted for a broad and interdisciplinary audience.