A K-Pop column by the name of 'Idology' recently published a full timeline of K-Pop's generations, starting with the founder of the 1st-generation H.O.T all the way through the new wave of 4th generation idols.
In this timeline, 'Idology' categorizes the generations of K-Pop by creating sub-generations - the 1.5 generation, the 2.5 generation, and the 3.5 generation.
You can find 'Idology's full analysis of the generation timeline here.
Damn, someone take me back to the "golden era" of kpop of 2009- SNSD, Big Bang, TVXQ, Shinee, 2pm, 2ne1, miss a, fx SUJU- damn, iconic songs were released that year!