Yeah, that’s the classic progression. Early CRTs were judged by line pairs per millimeter because the resolution was limited by the electron beam and phosphor dot spacing. Each line pair represented a black–white transition, so 50 line pairs per millimeter meant 100 lines, or about 50 vertical pixels per inch. As semiconductor displays emerged, we could count individual pixels, so the metric shifted to pixels per inch. With LCDs, the pixel pitch became the key figure. A 22‑inch 1080p screen has about 80 ppi, but a 27‑inch 4K panel bumps that to around 170 ppi. That jump is not just a number; it changes how sharp text looks and how much detail the eye can resolve. Today, with OLED and mini‑LEDs, manufacturers can squeeze more pixels into the same space without sacrificing brightness or contrast, so we’re seeing densities over 400 ppi on some ultrathin monitors. From a perfectionist’s viewpoint, the evolution is satisfying because it’s driven by measurable improvement—each increase in pixel density translates to a finer sampling of the image. The only trade‑off is cost and power consumption, but those are improving too. So in short, pixel density evolution is a textbook case of engineering delivering incremental, quantifiable gains that align with what a monitor critic like me can obsess over.