Marjorie Janice Groothuis Horning (August 23, 1917 – June 11, 2020) was an American biochemist and pharmacologist. She was considered to be a pioneer of chromatography for her work in developing new techniques and applying them to the study of drug metabolism. She demonstrated that drugs and their metabolites can be transferred from a pregnant woman to her developing child, and later through breast milk, from a mother to a baby. Horning's work made possible the prevention of birth defects, as doctors began to warn of the dangers of drugs, alcohol, and smoking during pregnancy. Early life and education Marjorie Janice Groothuis was born in August 1917 in Detroit, Michigan, to Nina Jane Potter and Herman Groothuis. She studied at Goucher College in Baltimore, Maryland, graduating with a Bachelor of Arts in 1938. She then attended the University of Michigan, graduating with a Master of Science in 1940 and a Doctor of Philosophy in 1943. She worked as a research assistant in the pediatrics department of the University of Michigan Hospital until 1945. Career Horning moved with her husband to the University of Pennsylvania in Philadelphia, Pennsylvania in 1945, working there until 1951. In 1950, Evan was appointed Chief of the Laboratory of the Chemistry of Natural Products of the National Institutes of Health (NIH) in Bethesda, Maryland. In 1951, Marjorie obtained a position as a research chemist at the National Heart Institute at NIH. She remained there until 1961. In 1961, the couple moved to Baylor College of Medicine in Houston, Texas. Marjorie became an associate research professor at the Lipid Research Center at Baylor. She became a full professor of biochemistry at the Institute for Lipid Research at Baylor College in 1969. In 1973, Atmospheric Pressure Chemical Ionization (APCI) first reported using a 63Ni foil and corona discharge by Evan and Marjorie Horning of Baylor College of Medicine. In 1974, Corona discharge at atmospheric pressure. DLI with effluent introduced directly from an LC column with APCI using 63Ni foil/corona discharge source, reported by Evan and Marjorie Horning, Baylor College of Medicine. In 1981, she became an adjunct professor of biochemistry and biophysics at the University of Houston, held concurrently with her position at Baylor. She worked on the editorial boards of Drug Metabolism and Disposition, Analytical Chemistry, Toxicology and Applied Pharmacology, the Journal of Chromatography, Trends in Pharmacological Sciences and Biopharmaceutics and Drug Disposition. In 1984, Horning became