1 the genetic material made from either DNA or RNA, long molecules that carry genetic information
2 a protein coat, called the capsid, which surrounds and protects the genetic material; and in some cases
3 an envelope of lipids that surrounds the protein coat when they are outside a cell. The shapes of these virus particles range from simple helical and icosahedral forms for some virus species to more complex structures for others. Most virus species have virions that are too small to be seen with an optical microscope. The average virion is about one one-hundredth the size of the average bacterium.