My thesis research involved Al-Sc alloys which were alloyed with Ti, Yb, Gd and Zr. These alloys form nanosize Al3Sc precipitates. Adding ternary and quaternary additions to the Al-Sc alloys resulted in improved creep properties and led to a more stable microstructure at higher temperatures (>0.7 Tm). The small size scale of the precipitates requires the use of a specific set of tools to study the microstructure. One of the main tools used for this research is the three-dimensional local-electrode atom probe (LEAP) microscope. This instrument gives near atomic resolution which allows us to see the position of individual atoms within the material. Transmission electron microscopy was also used to study the microstructure.