An adequate endometrial receptivity is a crucial factor for embryo implantation. We describe endometrial morphology (endometrial appearance or pattern, endometrial thickness, volume, and delimitation), based on the concepts and possibilities of the new ultrasound modalities (3-dimensional/4-dimensional ultrasound, automatic volume calculation, virtual organ computer-aided analysis, tomographic ultrasound image, inverse mode, and 3-dimensional Doppler angiography) as markers of endometrial receptivity.