The elements lying in the middle of the periodic table between the s-block and p-block elements are known as d-block or transition elements. The f-block elements are called inner-transition series. The d and f block elements introduce various essential topics to the students like general properties of the transition elements (d block), physical properties, variation in atomic and ionic sizes of transition metals, ionization enthalpies, oxidation states, magnetic properties, the formation of coloured ions and complex compounds. This chapter deals with elements of d and f block of the modern periodic table. In this chapter, students shall first deal with the electronic configuration, occurrence and general characteristics of transition elements with special emphasis on the trends in the properties of the first row (3d) transition metals along with the preparation and properties of some essential compounds. It will be followed by consideration of certain general aspects such as electronic configurations, oxidation states and chemical reactivity of the inner transition metals.