Every person who owns any assets at all has an estate. Your estate may fill a 50-room mansion, or it may all fit in a shopping cart. But upon your death, those assets must, by law, be properly distributed. Exactly how and to whom they are distributed depends on your estate plan or lack of a formal one.
Whether you realize it or not, you already have a backup estate plan. In California, it's called "intestate succession," a series of laws and rules that dispose of your estate in the absence of a will or a living trust. However, that might not be the estate plan that's best for you or for your family.
Without proper planning, a Probate Court may have to decide how your estate is divided according to state law. And that may not be consistent with what you actually wanted or intended. Even if your family "knows" that you wanted things a certain way, the Probate Court is bound by the intestate laws and none of what your family "knows" will matter. The way to prevent that problem in the first place is to create an estate plan that's right for you, so that you can keep control over the things that matter most to you.
It can never be too early to create your estate plan. But it can be too late.