This lecture covers the fundamentals of gradient echo contrast (T2*) in biomedical imaging, explaining the concept of T2* weighting and static dephasing. It also discusses the various contrast mechanisms in MRI, such as proton density, T1, and T2-weighted images, with examples from the Whole Brain Atlas site at Harvard. Additionally, it explores T2*-weighted images for venography and BOLD fMRI, as well as spatial encoding techniques in MRI.