Former South African President Nelson Mandela has been admitted to hospital after suffering from a lung infection.
He was taken to hospital on Wednesday night.
His doctors say he is doing well and responding to treatment.
Nelson Mandela is one of the most famous men in the world and a hero to many.
The 94-year-old's health has caused concern for some time.
In December he spent 18 days in hospital for treatment for a similar infection.
Who is Nelson Mandela?
Mr Mandela was elected president of South Africa in the country's first democratic elections.
He spent a lot of his life in prison after protesting against the way South Africa was ruled, a system called 'apartheid' which kept white and black people apart.
It meant that black people in South Africa had fewer rights and couldn't vote. White people controlled what jobs black people could have and even where they lived.
Mandela is now seen across the world as being responsible for helping to end apartheid.