This presentation covers the theory and practice of scanning transmission electron microscopy in a scanning electron microscope or STEM-in-SEM. It provides a detailed overview of the measurement physics, the equipment required, the importance of collection angle control, and contrast interpretation. It explains how and why different detectors are used and how they are calibrated. It addresses the issue of beam damage and explains how to quantify and deal with it. It also covers advanced concepts, including 4D STEM-in-SEM, nanoscale strain and temperature mapping, and the use of programmable STEM detectors for imaging and diffraction, and provides examples demonstrating the capabilities of the various measurement setups.