Welcome back!! This is the first lecture in my CEEN 641 Advanced Soil Mechanics course. In this lecture, I review three of the most important concepts in basic Soil Mechanics: Phase diagrams and phase relationships of all soils; Relative density of course-grained soils; and Atterberg limits and plasticity of fine-grained soils. We solve a complicated fill/borrow problem together, and I introduce you to some helpful resources from NAVFAC (i.e., the US Navy) for geotechnical engineering.