Methods for determining lipid composition. The lipid(s) in a composition may include phospholipids. A method may be carried out on an individual cell. A method may compare the Raman spectrum of the portion of a cell with a model Raman spectrum, which does not include the lipid component, where the difference between the Raman spectrum of the portion of the cell and the model Raman spectrum correlates to the lipid composition in the portion of the cell in the portion of the cell). A method may be used to diagnose a disease such as, for example, cancers, including breast cancer, prostate cancer, and via the presence and/or absence of abnormal or damaged cells in an individual.