Maggie Lieu is an ESAC research fellow working on Euclid, a visible and near-infrared space telescope due to launch in 2021. By measuring the shapes of distant galaxies we can determine the mass of the largest systems in the Universe, galaxy clusters. Euclid will achieve unprecedented shape measurements of galaxies covering almost half of the extragalactic sky.Maggie is developing statistical methods to deal with this upcoming big, noisy dataset, so that we can better understand the physics of galaxy clusters and their role in the Dark Universe.