We hear it all the time from others. "Call your grandparents." Sometimes we're told so much to our chagrin, or in spite of our reluctance. To preface; it's crucial to understand that it is a privilege to have solid mentors that happen to be your parent's parents. I understand not all grandparents are equally awesome, and like anyone else they're also human as well, so let's not over-glorify things.
Now that we've got the disclaimer out of the way let's get to the meat and potatoes of this. Who your grandparents are can be a small portrayal of where you've come from. They can tell you why you are the way you are sometimes and are also a great guidepost for genealogical history as well. Talking to your grandparents and your older relatives provide insight into how your family came to be, and they provide invaluable information about embarrassing things that have happened to your parents that they would never reveal to you as well.
They have ALL (and I mean all) of the old family cooking recipes, and you know you need to learn those ASAP. They can give you some sound advice at times too, since they've got a little more time lived under their belt, even if "they don't get it."
Personally, I've found that my grandparents have been one of my biggest sponsors in life as well. My grandparents picked me up from school from the time I was a little squat up until I was that annoying teen getting ready to drive for the first time. They've been to countless games, ceremonies, and birthdays, and they're always happy to be there too. It's hard to find bigger fans than your grandparents, maybe besides your parents. I've learned about where my family is from thanks to my grandmother, and there have been several times I've asked for, or have (sometimes unwillingly) received advice from my grandfather too that answers more about who I am than I had initially thought or intended to ask for.
They're a great compass to understand where you're going and what you've been through to get where you are.
I can't tell you how many "Back in my day.." stories I've had that give me a quick punch to the gut of reality to understand how hard it used to be, and what I'm fortunate to be dealing with today.
We live in different times, and those times are relentless in their pursuit of change.
Having grandparents to talk to about the difference of the times can collide with the differences we have together.
When you sit down and take the time to realize that without these people sitting in front of you, you wouldn't even exist you begin to try and approach the bigger picture of learning where you come from.
Take the time when you can to call them and ask them how they are. Even if it's for two minutes they will be the happiest people on Earth to see you're calling them. Nobody gets to spend the time we have together forever, so enjoy them while you're all still here if you ever get to that point in your life you'd be wishing the same.