The Thesis is devoted to precision spectroscopy in the extreme ultraviolet (XUV) region of the electromagnetic spectrum aided by the use of two nonlinear processes: stimulated Brillouin scattering (SBS) and harmonic generation. The former is used to efficiently compress laser pulses in order to achieve high peak intensities, necessary for enhancing the yield from a nonlinear process such as harmonic generation. The process of pulse compression by SBS is discussed in detail in the first part of the Thesis, both from theoretical and experimental perspective. The use of successive second and third harmonic generation for precision frequency measurements in the XUV is demonstrated as well. A laser system is being developed (the latest results are presented in Chapter 7) that combines both SBS pulse compression and harmonic generation techniques, and is expected to deliver narrowband (3x10^-6) wavelength tunable pulses in the XUV.