Competing and anisotropic interactions can lead to molecular systems self-organising as pressure or concentration is varied. We have recently discovered that Sr3Ru2O7 shows analogous behaviour (where a magnetic field takes the place of pressure or concentration). A magnetic field parallel to the tetragonal c-axis can tune the system to induce incommensurate antiferromagnetic order over a small range of field. The incommensurate phase has a number of unusual properties including a higher entropy than the neighbouring low- and high-moment ferromagnetic phases. It also displays nematic behaviour in that a field tilted away from the c-axis can induced strongly anisotropic transport properties. Here will propose to measure more magnetic Bragg peaks to determine the magnetic structure of the ordered state. We will also measure the order parameter as a function of field and temperature.