You are probably thinking of pelargoniums, a "cousin" of geraniums and a very common house plant. Hydrangea leaves are serrated and sort of heart shaped though.
The ones in the picture are hydrangea macrophylla mophead blooms. It is kind of early to be seeing blooms this open. Is it a picture from last year? Just walked around my hydrangeas and the flower buds are in the "broccoli phase". ;o)
