This book provides tools well suited for the quantitative investigation of semiconductor electron microscopy. These tools allow for the accurate determination of the composition of ternary semiconductor nanostructures with a spatial resolution at near atomic scales. The book focuses on new methods including strain state analysis as well as evaluation of the composition via the lattice fringe analysis (CELFA) technique. The basics of these procedures as well as their advantages, drawbacks and sources of error are all discussed. The techniques are applied to quantum wells and dots in order to give insight into kinetic growth effects such as segregation and migration. In the first part of the book the fundamentals of transmission electron microscopy are provided. These are needed for an understanding of the digital image analysis techniques described in the second part of the book. There the reader will find information on different methods of composition determination. The third part of the book focuses on applications such as composition determination in InGaAs Stranski--Krastanov quantum dots. Finally it is shown how an improvement in the precision of the composition evaluation can be obtained by combining CELFA with electron holography. This is demonstrated for an AlAs/GaAs superlattice.