The recent comeback of SISTAR19 has stirred up waves of nostalgia, taking us back to the golden era of early 2000s K-Pop. It's a perfect time to revisit some of the iconic groups that defined a generation and set the stage for today's global K-Pop phenomenon.

1. TVXQ: They were more than just a K-Pop group; they were a cultural phenomenon. TVXQ's impact on the Asian music market was unparalleled. With hits like "Rising Sun," "Triangle," and "Hug," their popularity knew no bounds. Their dynamic performances and catchy tunes left an indelible mark on the hearts of fans across the globe.

2. Epik High: Known for their deep, thought-provoking lyrics and unique sound, Epik High has evolved significantly over the years. Their early work, with songs like "Fly," "One," and "Love Love Love," showcases their journey from raw, emotional storytelling to the polished, versatile artists they are today.

3. SG Wannabe: This trio is remembered for their soul-stirring ballads and harmonious vocals. Their melancholic tunes, like those in "Lalala," resonated deeply with listeners, making them one of the most beloved vocal groups of their time.

4. Battle: Though their time in the spotlight was brief, Battle left a lasting impression with catchy tunes like "Step by Step." Their energetic performances and fresh sound made them stand out during their all-too-short time on stage.

5. Sunny Hill: Renowned for their eclectic concepts and music style, Sunny Hill was a breath of fresh air in an industry filled with similar concepts. Their gothic and unique themes set them apart, showcasing their versatility and creativity.

6. A'ST1: A'ST1 was a group ahead of its time, featuring international members in an era when such diversity was rare. Their unique composition and talent made them stand out, and their presence in today's global K-pop scene would be fascinating to see.

As we look back at these legendary groups, it's clear they laid the groundwork for the diverse and dynamic K-Pop industry we know today. Their contributions went beyond music; they shaped a cultural movement that continues to inspire artists even today. So, take a trip down memory lane, revisit these classics, and let us know your thoughts on these pioneers of K-Pop.