My research has concentrated primarily on stellar X-ray astronomy, with a special emphasis on stellar clusters (such as the Pleiades) and star-forming regions (like the Trapezium cluster in the Orion Nebula). One of the most important issues that can be addressed through these studies is determining what parameters (e.g., age and mass) most affect the stellar X-ray luminosity function. Mass-dependent spindown timescales give rise to age-dependent distributions of rotational velocities, i.e., rotation seems to be the key. Since the X-ray activity in a late-type star is expected to arise as the result of the magnetic dynamo, a relation between X-ray emission and rotation is not surprising. This research is carried out mostly with data acquired from satellite-borne imaging X-ray telescopes but also requires the use of optical and radio telescope facilities.