We have entered a golden era for time domain astronomy, particularly when it comes to variability studies of young T Tauri and Herbig stars. These 1-10 million year old young stellar objects (YSOs) occupy a key epoch in the evolution from molecular clouds to mature star/planet systems. Many of them host protoplanetary disks, from which gas accretion is mediated by complex magnetic field structure. At the stellar surface, hot spots form at the base of accretion columns, while cold spots appear as a result of local magnetic field structure. Dust orbiting within the inner 0.1-1 AU of the disk occupies clumpy structures, some of which may appear to occult the central star. Many years of ground-based monitoring studies have revealed that these phenomena contribute to high levels of variability in young stars, on sub-hour to year timescales. Yet only recently have we begun to link detailed time domain features with the structure and dynamics of YSOs and their surroundings.
In this talk I will review the astounding progress that we have made in classifying and understanding young star variability, thanks in large part to the rise of precision space photometry missions. I will focus on recent results from the K2 Mission's campaigns on several young clusters and associations, highlighting discoveries of accretion burst sources, obscuring dust clouds, and young planets. In the future, new surveys by TESS, LSST, and PLATO will expand our view of YSO variability to higher mass as well as into the brown dwarf regime.