A quantitative approach of electron microscopy is developed to measure local concentration and strain in quantum Structures obtained by hetero-epitaxy of III-V alloys. Quantitative analysis of TEM (200) dark-field image contrasts in InxGa1-xAs/GaAs planar layers was carried out to understand the evolution of strain and chemical contrasts as a function of In composition. The transmitted intensity profile across the InGaAs/GaAs layers is compared with Simulations that include a finite element approach of the 3D strain profile in combination with a dynamical contrast simulation. When InGaAs/GaAs layers are grown on V-groove substrates, a quantum wire is formed at the groove bottom. With this approach, an indium enrichment in these quantum wires can be identified. The In concentration is quantified in a more quantitative way using electron energy loss spectroscopy. In the quantum wire centre an additional 4nm wide In rich vertical layer can be identified. (C) 2002 Elsevier Science B.V. All rights reserved.