3/4 oz of Triple Sec
1/4 oz of Bailey's Irish Cream (or Irish Cream)
2-3 drops of grenadine syrup
Fill your shot glass 3/4 way full with triple sec. Carefully layer the bailey's on top of the triple sec, and add some drops of grenadine into the center. If done correctly it will look like an atomic mushroom cloud when the drop hits the bottom of the shot glass.