Step 1: Understand why the OSI model has layers at all. The OSI model breaks the huge job of network communication into smaller, independent stages, so that each stage only has to worry about one specific responsibility. Step 2: Walk through the stack from bottom to top. Starting from the hardware and working upward, Physical, Data Link, Network, Transport, Session, Presentation, and Application. A handy way to remember the order is the phrase All People Seem To Need Data Processing. Step 3: Count the layers you just listed. Counting each named stage from Physical up to Application gives exactly seven distinct layers. \[ \boxed{7} \]