Gray card : card with an 18 percent gray tint (reflectance) used to determine exposure by taking a meter reading from subject light reflected by the card.
Deoxyribonucleic Acid [DNA]
Deoxyribonucleic acid is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. DNA and RNA are nucleic acids; alongside proteins, they compose the three major macromolecules essential for all known forms of life.