Leaf hoppers belong to the order Hemiptera and the family Cicadellidae which is divided into over 40 subfmailies. This group includes many genera with more still being discovered.
As shown in the measurements at the far righthand side of this page, this is not a particularly lage piece of amber and it isn't much thicker than a quarter.

Leaf hoppers and similar insects belong to the suborder Homoptera which some entymologists consider a seperate order. Leaf hoppers are small but very common and this is a very diverse and often colorful group. This group includes many important pest species. Adaptive radiation has kept well ahead of the extinction rate so there are now far more species of leaf hoppers than in ages past. The leaf hopper shown here is about 25 million years old and so probably represents an extinct species. It would take an expert to confirm this, however.