The phrase "to scratch the surface" means to only explore or understand a small part of something, without going deeper or fully understanding it. Full definition
As you can see, this is just just scratching the surface of something that seems like it should have a simple answer. (dinesentax.com)
It has taken years to reach this point and we're still only scratching the surface of what we can do with this information. (social.hays.com)
This is really just scratching the surface of what is to come, next weekend we'll have more information regarding this exciting new expansion to a huge game. (thatvideogameblog.com)