The atomic interfaces between ferromagnetically ordered thin films with perpendicular anisotropy and either films with magnetically ordered in-plane anisotropy or a non-magnetic metal are responsible for nearly all the exciting physics leading to potential devices in areas as diverse as broadband THz generation, DMi and Skyrmions, Spin Hall effects, Spin torque/Vortex oscillators (STO) and data storage. Understanding the magnetic structure of these atomically engineered interfaces as a function of depth is a key element in optimizing layer structures and developing the underlying physical insight necessary for exploitation.