With incidence of atherosclerosis, hypertension and heart attacks on the rise; understanding of lipid metabolism has gained more importance than ever before. The chapter begins with classification of lipids into Simple lipids, Compound lipids and Derived lipids. Table 4.1 gives you normal serum lipid levels. One question that often arises in the mind of a common reader viz. ‘If cholesterol and other lipids are insoluble in water then how they are rendered soluble in serum?’ is explained in a logical manner. Various classes of lipoproteins those can be separated by ultra centrifugation method, i.e. High-density lipoproteins, Low-density lipoproteins, Very low- density lipoproteins and Chylomicrons are discussed. Zoom In box deals with a very relevant question \'Cholesterol: A Friend or A Foe?\' In relation to lipids you have to answer a lot of WHYs- \'Why atherosclerosis is considered a harmful entity? Why LDL is called as bad cholesterol and HDL as good cholesterol? Why sometimes it is seen that a person with high total serum cholesterol doesn\'t suffer from coronary artery disease but it develops in another person with a lower total serum cholesterol level?\' All these and more mechanisms are discussed in the light of scientific knowledge. The chapter concludes with a Zoom In on \'Dietary guidelines for healthy living\'. In short this chapter covers all the basics of lipids related to phenomenon of atherosclerosis.