Neat and tidy way to build simple circuits attached to a Pi Pico. The size is identical to the Pico, with useful tracks already on the board for connecting components. It can be directly soldered to the Pico, or (better) to a connected accessory, or (best) used with header pins.
Here is a simple circuit that I designed and built, to prevent "brown out" of a solar-powered Pico by holding the "RUN" line low until the battery has charged sufficiently to allow it to start up cleanly.