Imagine you’re buying a used car. Before you hand over the money, you’d kick the tires, peek under the hood, study the service records, and probably take it to a mechanic you trust. You’d want to be absolutely sure you’re not driving off with a shiny shell hiding a wrecked engine. When one company buys another, it works the same way — except the stakes are much higher. That careful, skeptical, show-me-the-proof investigation is what we call due diligence (DD). This chapter walks you through exactly what gets checked, why it matters, and how a thorough due diligence process can make the difference between a deal that builds value and one that destroys it.