Recent measurements of gravitational lensing by large scale structures initiated very optimistic previsions for the future of this area. I will first discuss the most promising theoretical aspects of cosmic shear and show how they constrain the cosmology, and propose some routes for future developpements. I will then talk about the recent measurements and show why it is so difficult. I will finish on the oncoming measurements taken place in our weak lensing survey which is currently in progress at the Canada France Hawaii Telescope.