mitxela has built an #LED matrix earring from 52 0201(!) LEDs (i.e. 0.65 × 0.35 mm footprint) on a 9 mm diameter circular PCB. Or rather, two PCBs soldered back-to-back because this density of components basically requires a four-layer PCB with blind and/or buried vias, which would've been very expensive. The video also features a "very cheap" (3600 USD) pick & place machine. I expect these to show up in makerspaces soon.
