This lecture is an introduction to the generation of plasma-based XUV lasers and their use as a source for scientific
applications. We first discuss the main conditions required to create population inversions and amplify XUV radiation.
We give an overview of the main properties of the different types of XUV lasers beams that are currently operational
worldwide, while comparing them to other ultrashort, high-brightness sources existing in the same spectral range. We
discuss recent demonstrations of applications of plasma-based XUV lasers to high-resolution imaging and interaction
with matter at high intensity. Finally we conclude with current prospects for extending these sources to shorter
wavelength and higher output intensity.