Robert Downey Jr. is paying tribute to the late Stan Lee on what would have been the Marvel creator's 98th birthday. As every Marvel fan knows, Lee passed away in 2018, and the pain of the loss continues to sting in 2020. Among those remembering Lee on his birthday is RDJ, who took to Instagram to post a photo of himself alongside Lee from the set of Captain America: Civil War.

"Are you Tony Stank?" writes Robert Downey Jr. in the caption, referring to Lee's memorable cameo in the movie. He adds, "#HappyBirthday Stan. We miss you..."

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Social media has also been filling up with thousands of tribute posts for Lee. The official Stan Lee account encouraged followers to keep the discussion going by sharing their memories of Lee using the hashtag #StanLee. The post reads, "Today we celebrate what would have been Stan's 98th birthday. Stan meant so much to his fans around the world & his fans meant a lot to him, too. We'd like to fill this post with wonderful memories of The Man, so please share your favorite Stan moments below. Excelsior!"

Marvel also paid tribute to Lee by publishing an article highlighting his body of work. "98 years ago today in New York City, a legend was born," the article reads in part. "Working with some of the best artists in the business, Stan Lee would create the larger-than-life characters in the pages of Marvel Comics. Characters and stories that have stood the test of time and continue to dazzle and amaze fans around the world. From fantastic families to amazing spiders to uncanny outcasts and even earth's mightiest, Stan Lee's vision lives on."

Echoing thousands of other tweets, one fan tribute post reads, "Happy Birthday to the brilliant mind that was Stan Lee! Thank you for bringing to life such marvelous characters and making my entire childhood. Excelsior!"

"Happy birthday to my all time favorite comic book writer, producer & many other things," another fan says. "Thank you for sharing your extraordinary imagination with us. We love you 3000. May your beautiful soul Rest In Peace."

Posting artwork of Lee, another fan writes, "Happy birthday Stan Lee, Thank you for making our childhood special with the heroes and stories you've created for us...may your soul rest in peace in heaven."

Lee's life and career were previously covered in the 2010 documentary With Great Power: The Stan Lee Story, and he could next have his story explored in an upcoming biopic. It was recently revealed that a script about Lee and Marvel collaborator Jack Kirby, dubbed Excelsior!, made it to the 2020 Black List. Written by Alex Convery, the story follows the "meteoric rise (and subsequent fall) of Marvel Comics and the star-crossed creators behind the panel." As an unproduced script, there's no guarantee at this time that the movie will be made.

In any case, it's clear from the social media response just how much Stan Lee is loved, missed and remembered since his passing. You can join in by sharing your own memories of Lee using the hashtag #StanLee on social media. The photo of Lee and RDJ was posted by Robert Downey Jr. on Instagram.