The object of this proposal is to investigate the mechanism of network collapse in the ¿strong¿ network glass forming system GeO2 in the pressure range between 9 and 16 GPa where the Ge-O coordination number changes from 5 to 6. The new experiment will complete our investigation of this system by neutron diffraction and will build on the progress in experimental technique that has been made. PEARL is the only neutron diffractometer which will allow access to this pressure regime. Complementary information on the structure will be obtained by using x-ray diffraction and the results will be interpreted with the aid of both first principles and classical molecular dynamics simulations. The structural changes that take place in GeO2 are similar to those reported for silica but occur at much smaller pressures.