We propose to realise the first experimental demonstration of gamma-ray coherent emission by means of super-radiance in a Bose-Einstein condensate of 135mCs isomers. The isomers will be produced by proton bombardment and will be then laser cooled and trapped in a magneto-optical trap. The cold atomic sample will be transferred to an optical dipole trap, where, by means of forced evaporative cooling, a Bose-Einstein Condensate will be realised. The 135mCs condensate will satisfy the requirements for gamma-ray coherent emission at 787 keV. The project will lead to several milestones in fundamental physics, thus triggering further novel researches, and will demonstrate the practical feasibility of gamma-ray lasers, that would have numerous potential applications ranging from energy industry to medicine.