represents a dark wedge. Sawhorse projections are used to view molecules from an angled perspective instead of a side view. The parallel bonds represent eclipsed conformations and all anti parallel bonds can represent either gauche or anti conformations. Newman projections are used to visualize molecules from front to back along a carbon-carbon bond. The carbon closest to the viewer is the front carbon and the one furthest away is the back carbon. The three atoms attached to the front carbon are depicted as being attached to the center of a circle and the atoms attached to the back carbon are shown as coming from behind the circle. Newman projections are often used as a simplified version of sawhorse projections. Significance Cahn–Ingold–Prelog priority rules are part of a system for describing a molecule's stereochemistry. They rank the atoms around a stereocenter in a standard way, allowing the relative position of these atoms in the molecule to be described unambiguously. A Fischer projection is a simplified way to depict the stereochemistry around a stereocenter. Thalidomide example Stereochemistry has important applications in the field of medicine, particularly pharmaceuticals. An often cited example of the importance of stereochemistry relates to the thalidomide disaster. Thalidomide is a pharmaceutical drug, first prepared in 1957 in Germany, prescribed for treating morning sickness in pregnant women. The drug was discovered to be teratogenic, causing serious genetic damage to early embryonic growth and development, leading to limb deformation in babies. Some of the several proposed mechanisms of teratogenicity involve a different biological function for the (R)- and the (S)-thalidomide enantiomers. In the human body however, thalidomide undergoes racemization: even if only one of the two enantiomers is administered as a drug, the other enantiomer is produced as a result of metabolism. Accordingly, it is incorrect to state that one stereoisomer is safe while the other is teratogenic. Thalidomide is currently used for the treatment of other diseases, notably cancer and leprosy. Strict regulations and controls have been enabled to avoid its use by pregnant women and prevent developmental deformations. This disaster was a driving force behind requiring strict testing of drugs before making them available to the public. Polysaccharide example The application of stereochemistry to biological macromolecules has allowed for the study of the structure and properties of polymers of biological origin. In regards to the degradation of starch and cellulose, D-glucose is produced by different intermediates which are