High-dimensional quantum states are desirable for the study of complex quantum systems and the development of quantum technologies. Yet, their implementation can be challenging as it is their characterization. In the first part of this talk, I will focus on recent progress in the generation of high-dimensional quantum states in photonic circuits. I will show how this approach can make the implementation of large quantum states flexible and scalable by exploiting the intrinsic advantages of integrated devices. In the second part of the talk, I will deal with the more general problem of characterizing large quantum systems. Specifically, I will present some recent results on the study of multi-qubit systems by means of threshold quantum state tomography, an approach that can significantly reduce the number of measurements necessary to reconstruct the whole state density matrix.