Calcium-aluminum rich inclusions (CAI) are small metal rich pebbles found inside primitive, thermally unprocessed, meteorites. CAIs are special in the meteoritic inventory. They formed at high temperatures and pressures and are believed to have condensed from a hot metal-rich gas close to the protosun. Absolute and relative isotopic dating indicates CAIs are the oldest solids in our Solar System produced in a brief time interval of up to ten thousand years. I will discuss what we currently know about CAIs, and present a novel model of CAI condensation embedded in a state-of-the-art numerical simulation of star formation. This detailed model makes it possible to link the meteoritic evidence to our understanding of star formation, with CAIs forming in a few thousand years just after the birth of the Sun under very special conditions, which were not repeated at later times, and it therefore constrains future models of the formation of our and other Solar Systems. I will also discuss how CAIs can be used as a tracer of the dynamics inside the young solar systems, where they trace the existence of large-scale circulation of material and the emergence of the gas-giants.