The Doodle is illustrated by Danish guest artist Mikkel Sommer who is based between Athens and Berlin. The work that gained Gram an global reputation was his development of a method of staining bacteria, to make them more visible under a microscope. During his time at the university, Gram served as an assistant in botany to the zoologist Japetus Steenstrup. Gram joined the University of Copenhagen in 1878 and graduated in 1883, earning an MD. He won an award for an essay on the size and number of human erythrocytes in chlorotics. After his graduation, Gram travelled through Europe to study bacteriology and pharmacology. His travels eventually led him to the lab of Karl Friedländer, a German microbiologist.
It was there that he discovered that by treating a sample of bacteria with a crystal violet stain, iodine solution, and organic solvent, he could see the structure of different types of samples. Cells that were considered to be "Gram-positive" have an abundance of a specific polymer (peptidoglycan) and few lipids (a distinct fat/oil biomolecule found in all living cells), unlike bacteria that are "Gram-negative".
Gram's discovery not only helps in the identification and classification of bacteria, it also helps decide the treatment of bacterial diseases. Bacteria that possess a thick cell wall remain purple and are called Gram-positive while bacteria with a thinner cell wall fail to retain the stain and are classified as Gram-negative. The Gram staining technique has single-handedly helped diagnose countless bacterial infections - notably, Streptococcus pneumococci, a Gram-positive bacterial pathogen that causes a variety of life-threatening illnesses.
He published these findings the very same year in a scholarly journal and included a modest dislaimer that his findings are defective and imperfect but he hoped it would turn out to be useful in the hands of future investigators.