What makes So Girls by Rainbow notable?

'So Girls' debuted at number five on the Gaon Album Chart, indicating a strong reception in South Korea. Its title track 'SO COOL' showcased a blend of pop and dance elements that became characteristic of the K-pop genre during this era, influencing subsequent girl groups. Released on January 1, 2011, 'So Girls' is Rainbow's debut album, marking their introduction to the K-pop scene. At this time, they were emerging from a rigorous training period under DSP Media, aiming to establish their identity in the competitive landscape of girl groups.