Which brain structures might be called little brain and big brain?

Little brain would be cerebellum and big brain would be cerebrum.

If looked grossly, the brain seems to be composed of a big and small portion. But if you divide it based on function, the big brain would have much more part because it has many functions. The bigger brain functions can vary from motoric, sensory, or language. 
The small brain only has a bit function in motoric and balance.

The punnett square is the device used to predict genetics.

Atissue is a group of connected cells that have a similar function within an organism.