  Formation of GMCs is one of the most crucial issues in galaxy evolution. I
will compare CO and HI in the LMC in 3 dimensional space for the first time
aiming at revealing the physical connection between GMCs and associated HI gas
at a ~40 pc scale. The present major findings are 1) [total CO intensity]
[total HI intensity]0.8 for the 110 GMCs, and 2) the HI intensity tends to
increase with the evolution of GMCs. I argue that these findings are consistent
with the growth of GMCs via HI accretion over a time scale of a few x 10 Myrs.
I will also discuss the role of the background stellar gravity and the
dynamical compression by supershells in formation of GMCs.
