More than eight million Raspberry Pi computers have shipped since the product launched four years ago.

The popularity of the $35 machine for hacking together software and hardware, or just for using as a budget PC, even took the creators by surprise.

This gallery shows every version of the Raspberry Pi released to date, including the Raspberry Pi 3, which launched this morning.

This image is of a prototype of a $25 computer put together by the Raspberry Pi's co-creator Eben Upton in 2006.

The board uses an Atmel ATmega644 microcontroller clocked at 22.1MHz, and a 512K SRAM. Nineteen of the Atmel's 32 general-purpose input/output pin lines are used to drive the SRAM address bus. The board could output a 320×240 resolution image to a display.