A Kabbalist, a Litvak, and a Chossid, Walk Into a Bar on Shavuos Night 

When did the Minhag to stay up Shavuos night start?
Amazing stories with the kabbalists (R' Yosef Karo, R' Shlomo Elkabatz, R' Chaim Vital, Etc.)
What should we learn?
Should you learn Mishnayos or is one specifically not supposed to?
Source Sheet (rb.gy/vwjbdd)
Shavuos