We are developing a tabletop extreme-ultraviolet source using high harmonic generation at Brigham Young University. The thesis goes over the theory of high harmonic generation using the three-step model. This tabletop source was designed for probing magnetic domains of iron nanoparticles. We present optimization of the 42 eV and 52 eV harmonics through phase matching. Phase matching consists of tuning the intensity of the IR beam and pressure of the gas medium. The target gas medium used for this thesis is argon. The 42 eV harmonic was optimized to 8.2 billion photons per second. This was used with a 1500 mm focal-length lens, 15 mm medium length, laser power of 1.53 Watts, and a pressure of 12 Torr of argon gas. The 52 eV harmonic was optimized to 1.5 billion photons per second with a 1500 mm focal-length lens, 20 mm medium length, laser power of 3.29 W, and 14.9 Torr of argon gas. There are two designs for selection of harmonics: 1) a tunable design consisting of a toroidal mirror and flat diffraction grating and 2) a set of normal-incidence extreme-ultraviolet mirrors designed for 42 or 52 eV photons. Magnetic imaging uses x-ray magnetic circular dichroism to obtain magnetic contrast and use it to visualize magnetic nanosystems. Therefore, the high harmonic source also needs to generate circularly polarized light. Generating circularly polarized high harmonics is possible with a bichromatic beam. This is achieved using an apparatus called the MAZEL-TOV designed by Oren Cohen’s group at Technion University in Israel. The MAZEL-TOV consists of a BBO crystal for second harmonic generation, a pair of pulse delay compensation plates, and a quarter-wave plate. These optics are placed inline with the laser beam. We have successfully optimized the circularly polarized extreme-ultraviolet harmonics with the MAZEL-TOV. A spectrometer was made to calibrate the harmonics in the MAZEL-TOV spectrum. The tabletop source was then used to demonstrated coherent diffraction imaging of two pinholes.