Any method to determine the nature, properties, or composition of lipids in a specified sample of tissue after removal of that tissue from the body. Lipids are a heterogeneous group of fats and fatlike substances, including fatty acids, neutral fats, waxes, and steroids, which are insoluble in water but soluble in nonpolar solvents. Among other biological functions, lipids serve as a source of fuel and are an important constituent of cell structure.