DDT is a powerful chemical pesticide that was once widely used to kill insects, especially mosquitoes that spread diseases like malaria and typhus. The letters stand for dichloro-diphenyl-trichloroethane, which scientists mercifully shortened because nobody wanted to say that whole name every time.

During World War II and the decades after, DDT seemed like a miracle solution. It saved millions of lives by wiping out disease-carrying mosquitoes in areas where malaria killed huge numbers of people. Farmers also sprayed it on crops to protect them from destructive insects. For a while, DDT was considered one of humanity's greatest weapons against both disease and hunger.

The problem emerged when scientists discovered that DDT doesn't break down easily in nature. It builds up in the environment, moving from insects to fish to birds to other animals. Birds that ate contaminated fish started laying eggs with shells so thin they’d crack before the babies could hatch. By the 1960s, some bird species were disappearing. Rachel Carson's famous book Silent Spring exposed these dangers and sparked the modern environmental movement.

Today, most countries have banned or severely restricted DDT use, though some still allow limited spraying inside homes to fight malaria where the disease remains deadly. DDT became a turning point in how humans think about chemicals: just because something solves one problem doesn't mean it won't create others.