EUV spectroscopy of active regions from view point of coronal heating mechanisms

I will discuss recent advances in our understanding of coronal heating properties in active regions based on new diagnostics combining spectroscopic observations and (1D/3D) modeling. Spectral line properties (intensity, Doppler shifts, broadening, and their spatial and temporal variability) provide very stringent constraints on heating properties. I will focus in some detail on coordinated Hinode/IRIS/SDO active region observations of nanoflare heated AR core loops to showcase the diagnostics potential of high spatial, spectral, and temporal resolution chromospheric/transition region/coronal observations, when coupled with modeling.