Interference microscopy encompasses a wide range of techniques when it comes to measuring the many aspects of surface structures. Utilizing interference microscopy for these types of measurements includes the advantages of rapid, non-contact operation and rapid data acquisition, often at data acquisition rates in the millions of 3D image points per second. Due to its uniqueness among optical areal measurement instruments, interferometry has the benefit of high sensitivity to surface structures. This article discusses the principles of interferometric dimensional metrology applied to surface features best viewed in a microscope. Download the full paper for information on these principles, instrument design, signal modeling, and performance characteristics.