Adobe Photoshop

Photoshop codified the interface grammar most image editors still borrow: a vertical tool palette on the left, dockable panels on the right, and a layered document in the middle where edits stack non-destructively. The Layers panel turned editing into a reorderable list of intentions, and the History panel made time itself scrubbable, normalizing fearless experimentation through deep undo. Tool options live in a context bar that changes with the selected tool, keeping a vast feature set addressable without burying the canvas. The cost of that power is modality — the same pixels behave differently depending on tool, mode, and active layer, a mental model newcomers must internalize. Decades of accretion show, but the panel-and-layer paradigm endures because it scales.