Becoming comfortable with the onslaught of genetic information requires a familiarity with genetics terminology and basic molecular genetics. Caring for the genetic health of our patients requires an additional appreciation of genetic testing and screening issues and new areas of study with strange-sounding names, such as proteomics, nutrigenomics, and epigenetics. This article provides an overview of basic genetic principles and terminology with applications to critical care patients. It lays a foundation to support understanding of the other articles in this issue. An appreciation of genetics (the study of heredity) and genomics (the study of the interaction of genes within an organism) has an important place in the knowledge base of every critical care clinician.