The exploitation and manipulation of quantum states of light play a key role in the development of quantum technologies. Photons exhibit quantum behaviour at room temperature, are resistant to noise and decoherence and offer many degrees of freedom, making them a promising platform in all the areas of quantum technologies: quantum communication, computing, simulation, and metrology. In this framework, integrated photonics plays a central role through the development of on-chip systems and many progresses in a wide variety of platforms have been reported in these last 2 decades. The elements required for any experimental setup can be divided in three main categories: generation of photons, their manipulation and their detection.