M dwarfs are the most abundant stars in the Galaxy and favored targets to search for Earth-like exoplanets in the solar neighborhood. Two outstanding close targets, Proxima Centauri and TRAPPIST-1, belong to this class. Studying the formation of planetary systems around young M-dwarf stars is essential to understand the architecture of our closest planetary systems. I will discuss our findings regarding a tiny (about 3 au in radius) protoplanetary disk around the pre-main sequence M-dwarf star XZ Tau B, first identified through Science Verification ALMA data centered on another star, and recently confirmed with new ALMA observations centered on this source. I will discuss on the relationship of this tiny disk with the compact multiple-planet systems discovered in exoplanet surveys.