Learn about the ominous sounding Diminished Triad and its inversions. It might sound strange by itself, but these Triads build unique tension in your playing when used correctly.
Being able to recall and identify Triads on any string set and from any inversion is an important exercise to do if you want to implement Triads in your improvisation.
Now that you've learned the triad shapes, it's time to understand how to seamlessly integrate them in your playing. The best way to do that is to use a song we can all sing in our sleep.