This chapter discusses the lipid classes, individual fatty acids, lipid oxidation, and hydrolysis products of lipids. Column chromatography on diethyl aminoethylcellulose is a valuable method for the isolation of complex lipids. Thin-layer chromatography routinely applied for the separation, identification, and quantification of lipids. Fatty acids are essential components of lipids. Gas-liquid chromatography is the most commonly used method for fatty acid analysis. Lipid extracts are converted into methyl ester derivatives by acid catalysis and base catalysis. Anisidine value determines the number of aldehydes generated during the decomposition of hydroperoxides. Lipid oxidation products interact with other food components such as amino acids, peptides, proteins, nucleic acids, DNA and phospholipids to form fluorescent compounds. Fluorescent compounds form as the result of oxidation of phospholipids or from oxidized fatty acids in the presence of phospholipids. Solid fat content of a lipid influences its sensory and physical properties, such as spreadability, firmness, mouthfeel, processing, and stability.