In this presentation I will concentrate on normal development of the white matter in the cerebral hemispheres. I will use images of tissue sections and foetal brain MR examinations to highlight the important changes occurring in the cerebral hemispheres of the second and third trimester foetus and their relationship with developmental abnormalities. I will then move onto the normal post-natal development of the hemispheric myelin detailing the minimum knowledge required in order to report MR brain examinations of the neonate and infant. A number of potential interpretive pitfalls will be discussed. Learning Objectives: 1. To understand the changes in MR signal characteristics found in the foetal, neonatal and paediatric brain as myelination progresses. 2. To understand why different approaches need to be made when performing MR imaging of the brain in those groups. 3. To appreciate the effects that myelination has on the ability to detect the more common brain malformations.