A new technique has its value as long as it is known what it measures, not only how it measures. Paradoxically the actual development and application of Spin-echo Small-Angle Neutron Scattering (SESANS) started before its measured quantities were fully interpreted. This publication provides a manual on the methodology and interpretation of the SESANS measurements. Chapter ‘Theory’ could also have been named ‘What SESANS actually measures’. Chapter ‘Experiment’ could have been named ‘What SESANS is actually able to measure’. The subject of this book, both theoretical and experimental, is focused on isotropic particles (solid spheres, shells and gaussian coils) and structures formed by spherical particles.