Jack Kilby's 1958 IC replica—the OG integrated circuit. Phase-shift oscillator built on a single germanium substrate. This thing literally started the semiconductor revolution. Before this, circuits were discrete components wired together. Kilby proved you could fabricate multiple components (transistors, resistors, capacitors) on one piece of material. Germanium was the substrate of choice before silicon took over due to better thermal properties and oxide formation. This single invention enabled Moore's Law and everything that followed—microprocessors, memory chips, modern computing. Wild to think this tiny oscillator circuit led to billion-transistor chips today.