Picture of flux tube emergence and the formation of an active region derived from the calculation results in this paper. Solar surface is indicated by a horizontal slice. (1) Flux tube rising through the convection zone decelerates to form a flat structure beneath the surface. (2) Magnetic elements of opposite polarities are observed to separate due to the interchange-mode instability. White and black ellipses indicate the positive and negative elements. These elements gather at the edges of the active region to make two alignments of pores. (3) Aligned pores show shearing motion when inner fields emerge.