Dementia, such as Alzheimer’s and Parkinson’s diseases, is one of the biggest killers in developed countries. We are working on proteins involved in dementia to understand their biological function and to use this information to develop drugs to treat these devastating diseases. We use X-ray crystallography at the Australian Synchrotron and cryo–electron microscopy at the Bio21 Institute, University of Melbourne, to determine the 3D atomic structures of these proteins as a basis for designing experiments using molecular and cell biology approaches to probe their function. We then use the structures as the basis for rationally designing drugs. A major current focus is on cell surface receptors found on microglial cells, the immune cells of the brain, since there is accumulating evidence that these cells play a central role in many neurodegenerative diseases. Thus, the receptor molecules might be novel targets for developing new drugs that modulate the activity of these immune cells in disease.