Submerge the egg in cool water and watch In 48 to 72 hours and keeps growing to 5 inches in lengthGreat way to teach measurement Beginning egg measures approx 2.5 inchesJust completely submerge your 2.5 inch turtle egg in a glass or bowl of water,and wait. Within 12-24hrs, cracks will start to appear in the shell of theegg. And within 48 hrs, you will have hatched your very own baby tortoise.Leave it in the water, and it will continue to grow Once you take it out ofthe water though, after a few days it will start to shrink back down to itsoriginal size. Just put it back in the water, and it will start to grow again Tortoise colors may vary Growing animals and other things (brains etc ) thatare made to increase in size in water are made up of two polymers. One ispoly(vinyl acetate) which keeps the original proportions and shape of the itemor creature, and the other polymer is polyacrylamide which is the superabsorbent polymer. The growing creatures have many teaching applications inscience and math, including graphing, drawing conclusions, and measurementusing linear, mass and volume. The Growing Creatures Book by Anne Linehan andBetsy Franco details measurement and data collection projects integrating mathand science. Recommended for ages 6 and up