The development of a laboratory X-ray laser has been intensively pursued since the 1970s, and more so since its unambiguous demonstration in the 1980s. One of the aims of this area of research is the imaging of fast nanoscale objects, including small biological specimens. This comparison shows the successful evolution of this process, towards the experimental demonstration of saturation and the excitation of X-ray wavelength around the carbon edge (also known as the water window). From the 1990 it was clear the need of developing this technology at the scale of a table-top experiment.