We report on plan-view transmission electron microscopy techniques, by which the size, the actual shape and the strain of a coherent island in semiconductor heterostructures can be measured accurately. The bright-field suppressed-diffraction imaging condition where no strong diffracted beam is excited in the sample provides reliable size measurement as well as the detailed shape and aspect ratio. An exact two-beam diffraction condition is employed to produce the strain contrast of a coherent island and the corresponding fringes can be easily utilized to measure the average strain relaxation occurring during island evolution. We also propose an off-axis z contrast technique for the unambiguous determination of composition profile in an island. Finally examples of application of these techniques on the characterization of Ge coherent islands on Si(1 0 0) substrates are demonstrated.