Conducting studies in vitro—a Latin term that literally means "in the glass"—is essential in the fields of medicine and biology. Working with in vitro cultures is a relatively cost-effective and easily repeatable way of gaining insight into the interactions between cells or microorganisms and specific chemical compounds, such as drugs, nutrients, and toxins. However, to properly assess the toxicity of a compound, a reliable and efficient way to distinguish live cells from cells killed due to toxicity is necessary.