Prominent Kenyan academic Calestous Juma has died in the United States at the age of 64, prompting an outpouring of grief and tributes on social media.
"Intellectual giant", "innovator", "tireless champion of the world's poorest" - these are just some of the words used to describe the Harvard University professor after news of his death broke out on Friday.
Juma, whose research and writing focused on science and the environment, was a passionate advocate of the role of technological innovation in transforming African countries.
Earlier this year, he was named among the 100 Most Reputable People on Earth by Reputation Poll, a South African consulting company. Juma was also repeatedly included in the annual list of the 100 Most Influential Africans by the New African magazine.
His lawyer, Peter Wanyama, told Kenyan newspaper Daily Nation that Juma was "unwell for two years" and was undergoing treatment in the US city of Boston when he passed away. Wanyama did not specify the cause of Juma's death.
Kenya's President Uhuru Kenyatta offered condolences on Twitter, saying he was dismayed by the news of the professor's passing.
"We have lost one of our most distinguished scholars and patriots," Kenyatta wrote.
Paul Kagame, Rwanda's president, said the world has "lost a brilliant mind who was dedicated to innovation, education and Africa's prosperity".
Amina Mohamed, Kenya's foreign minister, described Juma as a "friend, compatriot and a role model".
"The best of the best", wrote fellow Kenyan academic Makau Mutua. Juma was a "towering scholar and a great human being", he added.
A former student, Farai Gundan, said Juma was a "great mentor" whose office was "a haven for discussions on [Africa] and its development".
The Bill and Melinda Gates Foundation, which has funded some of Juma's work, said he was "a tireless champion for economic and social development in Africa".
A prolific author, Juma published more than a dozen books on sustainable development and won several international awards for his work on the subject, Harvard said.
His latest book, Innovation and its Enemies: Why People Resist New Technologies, draws on nearly 600 years of economic history to explain how new technologies emerge and take root.
His writings have also appeared in Al Jazeera, as well as The New York Times and The Guardian.
Juma served on the jury of the Queen Elizabeth Prize for Engineering, among others, and was elected to several scientific academies, including the Royal Society of London and the US National Academy of Sciences.
Tributes also flowed in from politicians, journalists, celebrities and academics.
Here's a sample of some of them: