Research in chemical induction seeks to identify the compound or compounds responsible for differentiation in a developing embryo. Soren Lovtrup compared the search for these compounds to the search for the philosopher's stone. It was based on the assumption that the differentiating agents have to be chemical substances either within cells or in the extracellular matrix. However, despite numerous efforts to understand them, the nature of these substances remained largely a mystery from the 1930s until the 1980s, when the new era of molecular induction based on molecular genetics provided a new perspective. During the period of emphasis on chemical induction, a variety of different experiments were conducted aimed at discovering the chemical nature of the inducer. In some experiments, the organizer region was killed by heat to assess the inducing ability of a dead organizer. Other experiments used natural and synthetic compounds to attempt. Although none of these experiments identified a chemical inducer with any certainty, they did discover many related properties of the developing embryo.

Mary Frances Lyon studied gene expression and developed the theory of X-chromosome inactivation, also called Lyonization, during the twentieth century in the United Kingdom. The Lyonization hypothesis proposes that, even though females have two X-chromosomes and males have only one, one X-chromosome in females is always randomly inactivated, which causes males and females to have the same level of X-chromosome gene expression. Prior to Lyon’s hypothesis, scientists understood that there must be a biological way to compensate for the difference in X-chromosomes in males and females, but they did not know the exact mechanism. To investigate the topic, Lyon studied coat color in mice, a trait influenced by genes on the X-chromosome. Her resulting hypothesis highlighted X-chromosome inactivation as a mechanism for controlling gene expression in females without altering their DNA sequence. Through her research, Lyon aided scientists in understanding X-linked disorders, which laid the foundation for the development of gene therapies designed to treat X-linked disorders that affect hundreds of thousands of people globally.