Researchers are using new techniques from genomics called "DNA chips" or "DNA microarrays" to find out when and how genes are turned on or turned off during development or after a treatment, including treatment with drugs or toxins. DNA microarrays are like miniature pegboards, with each dot on the pegboard representing a test for a specific gene. A pegboard with 300 rows and 100 columns of pegholes has 30,000 peg holes. A miniature DNA microarray with 300 rows and 100 columns of dots has 30,000 dots, or enough dots for 30,000 genes. This amount of microarray can fit in an adult's hand.

Such DNA microarrays enable researchers to generate lots of information on how cells respond to treatment. Researchers and regulators have begun to figure out how to use this type of information in assessing the usefulness of drugs and the toxicity of chemicals in general. One difficulty in such assessments is that merely turning a gene on or off may not make a drug useful nor make a chemical a toxin. This field and this issue will be developing over the next few years, with impacts on pharmaceuticals, toxicology, food science and nutrition.