The common, apparantly circular morphology for many HII regions may indicate that HII regions expand almost uniformly and form 3D bubbles. Then, the small morphological differences between bubbles are likely caused by evolutionary effects coupled with density variations in the ambient medium. However, the detailed three-dimensional morphology of bubbles is still unclear. Using Herschel observations Anderson et al. (2012) found that 20% of the total FIR emission of bubble HII regions comes from the direction of bubble interiors, the locations inside the photodissociation regions (PDRs), which suggests a three-dimensional morphology. RCW120 is among the closest HII regions to the Sun, just 1.3 kpc distant. The extention of the ionized gas is 7.5 arcmin (3.8 pc) in diameter. There are numerous massive condensations along the PDR and star formation in the fragments in the shell may have been triggered by the expansion of the HII region, although the simulations in Walch et al. (2015) suggest that they merely reflect density inhomogeneities in the cloud from which the HII region formed. Recent studies (Torii et al. 2015) suggest that the exciting O-star in RCW120 was formed by a collision between the present two clouds at a colliding velocity ~30 km/s.