When starting baby-led solids it is recommended to offer your baby "french fry-shaped" foods. That's because anything smaller than that: a) is nearly impossible for a baby to successfully pick up and put in their mouths, b) could pose a choking hazard. Once your baby has developed a pincer grasp, however, a whole new world opens up to them. When babies fingers can pincer small items it's a sign that their mouths have also matured to the point where smaller foods become safe. You obviously want to still avoid hard, round items (candy, nuts, hot dogs, whole grapes, etc).
Blueberries are not for the immaculately dressed infant!
We never got the chance to introduce Buttercup to fresh blueberries, since they were in season before she was capable of safely handling them. However, now that her pincer grasp skill is firmly developed I got some frozen ones and they have proven to be a huge hit. If you are going to use frozen blueberries for your little one I'd recommend going organic, as frozen blueberries can pack quite the pesticidal punch (even more than your average non-organic produce).
Anyway, because they had been frozen these berries were quite soft when thawed, so they were really easy for Buttercup to chew. In fact, I've never seen her eat anything so fast. She was literally eating them hand over fist. I am thankful that I put two bibs on her, though, because her outfit would have been destroyed by the purple juice.
PROS: high nutritional value (antioxidants!)
CONS: non-organic is high in pesticides, very messy