There are two squares that are different from the average Jo square in Expansion Jo. They are the Grower, and the shrinker. When any player hits a grower, they grow one size, and when they hit a shrinker they shrink one size. The basic size, is 1x1, which is what every player starts out as. When you grow, you grow to become a 2x2 square, which means that you take up 4 squares total in a 2x2 grid. When you move in this form, you must move 2 squares in any direction, and then shade in a new 2x2 square. You can grow as big as 3x3 or as small as 1/2x1/2.

If you attempt to grow smaller than 1/2x1/2, then you lose the game, and you dont shade in the last shrinker that you stepped on. If you attempt to grow bigger than 3x3, you shade in a 4x4 box, and kill anyone in an 8x8 box centered on your 4x4 box. Then you die, after you kill everyone around you! On a small board, a person who explodes and grows to 4x4 can usually kill many people, giving him a high place.

When you step on a grower or a shrinker, and in changing happen to encapsulate someone else, then they lose the game and you shade over them. In order to move onto a grower or shrinker, you may not move on top of someone else, unless hitting the grower happens to move you on top of them.