Phones. The absolute pinnacle of engineering. Mining, materials science, cutting edge, chip design manufacture, international logistics and supply chain manage

Phones. The absolute pinnacle of engineering. Mining, materials science, cutting edge, chip design manufacture, international logistics and supply chain management, quantum physics in the display, relativity in the GPS, some very complex data compression and coding schemes in the modem, adaptive noise cancellation for voice and video, a global backend of satellites, fiber optics, and microwave/radio distribution for the comms infrastructure, a global collection of server farms and connection protocols, OS design and computer science in the software, a common-ish standard for browsers, AI and adjacent systems for image and video processing - and the whole thing spends most of its time serving ads and distributing cat videos.