Jeelabs shows how to in 2 parts use a STM32L0 Discovery board to measure current from 50mA to 100nA … that’s 10^6 range! Use on board shunt resistor and LCD display.
Ttechnoblogy.com shows a way to measure very small current, from 10µA down to 30 nA, using a discharge capacitor. The author uses a Atiny84 but it’s transposable simply to Forth with STM8 or STM32. Added to my todo list!