American technology company Tesla has launched sales of its new solar roof. The roof is made of glass tiles that can collect energy from the sun. The tiles were designed to make the roof look similar to those on traditional homes. Some of the tiles have solar cells inside that take energy from the sun and turn it into electricity. All the tiles look the same and the solar cells are invisible from the street. Tesla founder Elon Musk says his goal was to create a solar roof that looks better, costs less and lasts longer than non-solar roofs. The tiles are three times stronger than non-solar tiles, and weigh half as much, according to Tesla. The company is guaranteeing the tiles for the whole lifetime of a home.