Understanding the physical properties of the twisted active region ux tubes produced in the solar interior and how they emerge into the solar atmosphere is critically important for understanding the magnetic nature of the observed solar activities. I will present new results from 3D spherical she... Show moreUnderstanding the physical properties of the twisted active region ux tubes produced in the solar interior and how they emerge into the solar atmosphere is critically important for understanding the magnetic nature of the observed solar activities. I will present new results from 3D spherical shell simulations of the buoyant rise of active region flux tubes in the solar interior, which put a further constraint on the twist of the subsurface tubes in order for them to emerge with tilt angles consistent with the observed Joy's law. I will also give an overview on recent 3D simulations of the emergence of twisted flux tubes from the top layer of the solar interior into the solar atmosphere and corona and discuss how they provide explanations for some basic observed features in emerging active regions on the photosphere and in the solar corona. Show less