An artist has given thousands of yellow balloons to Kenyan commuters to take to work and counter their Monday-morning blues.
The BBC's Kevin Mwachiro says people getting off minibus taxis at Nairobi's central station looked somewhat bewildered to be handed the balloons.
Yazmany Arboleda, the US artist behind the stunt, told the BBC Monday mornings were usually a heavy moment for people.
He said he wanted to give away 10,000 balloons to change this perception.
"The big idea is to insert the iconography of celebration... [into] the habitual nature of working life," he told the BBC's Network Africa programme, as a team of his helpers handed out the balloons to hundreds of workers arriving by matatu taxis in central Nairobi early on Monday morning.
"We're celebrating them as they go to work and explaining that art is not just a photograph or a sculpture or a painting - it is this choreographed set of balloons as they spread throughout the city."
Kenya has been on high alert for the last three weeks since the government sent troops to Somalia in pursuit of al-Shabab militants it blames for a spate of recent kidnappings.
Since then there have been two grenade attacks in the city, blamed on sympathisers of the group.
"I find that this work is even more significant now that Kenya's social climate has been dampened by the al-Shabab threats and the recent attacks," Mr Arboleda said in a statement.
"I believe strongly that countering grenades with balloons could send an important message to the Nairobi community and the world at large," he said.
He said the balloons handed out in Nairobi were a living sculpture, part of his worldwide installation called "Monday Morning".
Nairobi is the third city he has given away 10,000 balloons during a Monday-morning commute. Over the last year, orange ones have been handed out in Bangalore, India, and green balloons to residents of the Japanese city of Yamaguchi.
As part of the continuing project, he plans to dole out balloons in four more places - in Europe, Colombia, Australia and finally New York.