In Vitro Testing refers to experiments conducted outside of a living organism, typically in a controlled laboratory environment. This method often uses cells, tissues, or biological molecules to study the effects of drugs, chemicals, or other substances. It allows researchers to observe biological processes without the complexities of a whole organism. This testing approach is crucial in fields like pharmacology and toxicology, as it helps identify potential side effects and efficacy of new treatments. By using cell cultures or organ-on-a-chip technologies, scientists can gather valuable data while minimizing ethical concerns associated with animal testing.