you put water in the base and the eggs in the holder then put dome over whole and the eggs get steamed - these are nice - you just have to figure how many minutes (book should say) to get your eggs boiled the way you like...Hard boiled longer obviously than say, soft boiled...I had one and loved it...used it so much I wore it out I guess cause after a year it died...lol...good luck. nice listing...fanned you - please fan back - k?