Ultra-Faint Dwarf Galaxies (UFDs) are the least luminous systems and also the least metal- enriched systems.
Their simple, ancient nature, gives us an opportunity to look back at the star formation activities in early galaxies.
In this talk, I will present the results of our highly-resolved cosmological ab-initio simulations to show how first galaxies
can be connected with their local descendants. Our work has, for the first time, traced the detailed enrichment history of