The Arduino UNO and Arduino Mega 2560 update the Duemilanove and Mega respectively. They now use an ATMega8U2 instead of an FTDI USB to serial converter chip. Allowing an Arduino to become nearly ...

First there was the realization that code could be run on the chip itself ... the ESP32 into a USB host. USB is not a native feature on all microcontrollers or even Arduino-compatible boards.