An ice core sample is a thick column of ice, sometimes hundreds of feet long, that is produced by drilling a circular pipe-like device into thick ice and then pulling out the cylindrical piece. Ice core samples from places like Greenland and Antarctica provide scientists with important clues about past climates. Air trapped in the ice remains there for thousands of years, so when scientists collect ice cores they can analyze the air to determine the composition of the atmosphere at the time the ice was formed. Sediments and tiny bugs are also found in the ice and provide additional clues to the state of the natural world at the time the ice was deposited.