The world celebrated Dr. Seuss Day on Monday, which marked what would have been the 111th birthday of the author, born Theodor Seuss Geisel.

Geisel was born on March 2, 1904, in Massachusetts and worked in many different fields before finding his niche as a children’s book author. Geisel would go on to become one of the most celebrated American authors, penning classics Green Eggs and Ham, The Lorax and Cat in the Hat, among countless others.

Celebs Celebrate Dr. Seuss Day

Happy Birthday Dr. Seuss! #ReadAcrossAmerica pic.twitter.com/EPHIHH9jzS

— HelloGiggles.com (@hellogiggles) March 3, 2015

“Today you are you! That is truer than true! There is no one alive who is you-er than you!” Happy Birthday Dr. Seuss. pic.twitter.com/8a6sEL6mrd

— History In Pictures (@HistoryInPics) March 2, 2015

Happy birthday, Dr. Seuss. Happy birthday to you! And to Flurny-bop Jones. And Fleeny McGrew!

— Joshua Malina (@JoshMalina) March 2, 2015

“Why fit in when you were born to stand out?” ― Dr. Seuss #HappyBirthdayDrSeuss

— Cory Booker (@CoryBooker) March 2, 2015

Dr. Seuss was one awesome grown-up. pic.twitter.com/cFpq5OtyA9

— Kid President (@iamkidpresident) March 2, 2015

In honor of #TheodorGeisel and his birthday – a picture of some of my first edition #DrSeuss books #HappyBirthdayDrSeuss

A photo posted by Sarah Michelle (@sarahmgellar) on Mar 2, 2015 at 2:47pm PST

New Dr. Seuss Book

It was recently announced that a new Dr. Seuss book will be published in July, based on a manuscript found after Geisel’s death. The book, titled What Pet Should I Get? will be released on July 28, and is one of three new Seuss books expected in the coming years.