Arduino Uno R3: Assembled from Arduino's Open UNO-TH Rev3e Design Files and Flashed over ICSP

The Arduino Uno R3 is open hardware: Arduino publishes its schematic and board layout. This blueprint builds one from those files, part by part, then loads the firmware into its two processors. Result: an Arduino Uno R3. An ATmega328P (16 MHz, 32 kB flash, 2 kB SRAM, 1 kB EEPROM) runs your programs; an ATmega16U2 turns USB into its serial link. It runs from USB (5.5 V at most) or 6-20 V at the DC jack. Source: Arduino UNO-TH_Rev3e design files and the A000066 schematic and datasheet (Arduino, CC BY-SA). Unknown: how every bought part is made; no public source in hand says. The soldering method is ours. Picture: Wikimedia Commons.