Russia's most famous prisoner, Mikhail Khodorkovsky, turns 50 on June 26.
Friends and well-wishers across the world are taking part in a birthday-letter-writing campaign
organized by Khodorkovsky's press center in Moscow.
The short personal messages will be printed out and handed to the jailed former oil tycoon on his birthday.
Khodorkovsky's spokeswoman, Olga Pispanen, says more than 2,000 people have already sent in their wishes.
"We thought long and hard about what would make Mikhail Borisovich, a man who is unable to communicate with people, happy," Pispanen says.
"We thought what he would like best would be to receive letters from people -- both people he knows and strangers – expressing words of support and wishes, for him to understand that people remember him and are waiting for him."
As part of the campaign, some of Khodorkovsky's acquaintances appeared in emotional video clips to complement their letters. Various luminaries and media outlets have been releasing a video per day in the run-up to his birthday.
Natalya Gevorkyan, a prominent Russian journalist who co-authored a book with Khodorkovsky, recorded her clip at a cafe terrace.
In the video she says: "Dear Misha. Here, in the free world, you have everything you need for happiness -- a beloved and loving family, friends. My wishes are about what is behind the [prison] wall. Come out of there alive and, as far as possible, healthy. You have a long life ahead of you, and I really hope it will be just as full and successful as the one we wrote about in our book. And in this future life that awaits you, please, astonish us."
WATCH: Journalist Natalya Gevorkyan sends her message to Mikhail Khodorkovsky.
Ordinary well-wishers, too, featured in the clips. Andrei Chernyshev and his wife Arina volunteered to be filmed as they wrote a letter to Khodorkovsky in their Moscow apartment.
Chernyshev says: "Dear Mikhail Borisovich, happy birthday. You don't know us, but we have been keeping track of your fate for many years. We admire your ability to save face and retain your human dignity despite exceptionally harsh conditions."
Prisoner Of Conscience
Khodorkovsky this year also marks the 10th anniversary of his detention.
The former head of the Yukos oil firm was arrested in October 2003 and jailed the following year on fraud and tax-evasion charges. In December 2010, he was convicted of additional fraud charges.
Yukos was broken up and sold off, mostly into state hands.
While many Russians have little sympathy for the former oligarch, once the country's richest man, Khodorkovsky is also widely seen as a political prisoner unfairly jailed for his political ambition and his stinging criticism of President Vladimir Putin.
Amnesty International considers him a prisoner of conscience.
Khodorkovsky is currently serving his sentence at a prison in the northwestern Karelia region, near the Arctic Circle. He is due to walk free in October 2014, although there is growing speculation that Russian authorities are preparing fresh charges to keep him behind bars.
His business partner, Platon Lebedev, is scheduled to be released in July 2014.
RFE/RL's Russian Service contributed to this report