A woman hangs up her washing in the Kibera slums as water bottles sit on her roof in the sun. Many diseases in developing countries are a direct or indirect result of drinking dirty water. One simple solution to this health problem may be an initiative by a Swiss researcher, Martin Wegelin, who is convinced that sunlight (UV radiation) can kill most bacterials. He claims one day of exposure to sunlight makes the water from a plastic bottle bacteria free. Martin Wegelin is co-ordinator of the...

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

People on horses riding through a forest alive with monarch butterflies. Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Ro...

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....

Every year, from January to the end of March, millions of monarch butterflies make a 4000 kilometre migration to breed in El Rosario where the world's largest colony of monarch butterflies are found....