It's incredible to think that Dr. Seuss - the children's book author who was born as Theodor Geisel - wrote his last book in 1990.
Even decades later, his classic stories are still bestsellers around the world.
It's easy to see why: Seuss books are fun, silly, and contain some important messages.
Seuss said that he never wrote for children, "I write for people."
And it's true that his books have important lessons for all of us.
1. On being true to yourself
Dr. Seuss understood the simple but meaningful fact that you can't be anyone except yourself.
Embrace your individuality, and the things that set you apart from the crowd.
When you accept the things that make you different from everyone else, they become your strengths.
2. On staying humble
One of Seuss's favorite topics to write about was learning, and that includes admitting we always have more to learn.
The person who insists he knows everything will never grow or change.
Seuss reminds us that we can all learn something, no matter what we think we know already.
3. On a person's importance
Empathy is one of society's most undervalued traits.
It's easy to see that if everyone was more caring and considerate towards each other, the world would be a better place.
Take a lesson from Seuss, and remember that a person is a person, no matter what.
4. On the value of humor
Many of Seuss's most famous books looked at very adult topics like war and environmentalism, but from a lighthearted perspective.
In our own lives, taking a step back from our problems and seeing the funny side of life reminds us what really matters.
It can also reveal unexpected ways to fix things - or put them back in whack.
5. On the power of learning
Of course an author would say so, but reading really is powerful.
It's an affordable way for anyone to grow, change their lives, and discover new perspectives.
In fact, we know plenty of books that can change your life for the better.
6. On limiting ourselves
We all know someone who's happy to sleepwalk through life "with their eyes closed" - maybe you're guilty of it too.
It's not just about stopping to smell the roses and appreciate the sunshine.
7. On life's limitless possibilities
When was the last time you went to bed feeling genuinely positive about tomorrow?
We like to get wrapped up in our problems, but the truth is that every day is full of limitless possibilities.
All you can do at the end of the day is remember the fun you had, and look forward to doing it all again tomorrow!
8. On practicing gratitude
Research actually shows one of the most effective ways to be happy is to practice gratitude.
By counting your blessings every day, you remind yourself of everything that makes your life special.
I bet you have a lot more to be thankful for than you even realize.
9. On your limitless potential
Your destiny is in your hands, and that's important to remember.
You may think that you're limited by what you don't have, or you don't know.
But this quote is a good reminder that the path to success is already inside you. It's up to you to start walking.
10. On resilience
Every once in a while, you have to stop and look back on everything you've been through in your life.
It's nice to realize that no matter how bad you've been hurt, and how bad you felt at the time, you're still standing!
You're a lot tougher than you realize, so don't beat yourself up for how you look or feel!
11.On trying new things
As children, we're always trying and learning new things. But adults are a little more set in their ways.
Variety is the spice of life, and it's also the only way to meet new people and discover new places.
So set out to tackle something "you never did" as often as you can.
12. On nurturing your inner child
As Seuss said, he only wrote for people, not children.
By now you probably realize what he was trying to teach us with his stories: to embrace creativity, learning, and discovery.
Seuss realized that most adults abandoned those qualities in their childhood - which is a shame.
The friendliest, warmest, and most interesting people are the ones who are in touch with their inner child.
13. On work-life balance
With our busy schedules, all of life's problems have a nasty habit of getting twisted up together.
When you spend time with your family, but you're busy thinking about work, they're only getting a fraction of the real you.
Leave work for work time, and when you're off the clock make time for everything else.
14. On the power of creativity
If you need any proof that creativity can change the world, just look at Dr. Seuss and his incredible success.
With just a pen, a paper, and his thoughts, he taught children around the world to be kind and curious.
Who knows what "thinks" you can think up if you set your mind to it?
15. On caring
After all of those reminders about embracing your creativity and caring, it's also important to remember you have to get things done.
Unless you take all of that self confidence and apply it every day, you won't change the world.
Take it from another bright thinker, anthropologist Margaret Mead:
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has.
For more words of wisdom, try the 15 things Winnie the Pooh can still teach us.
And be sure to read the 12 quotes from inspiring women you need to hear.