Expandable devices and methods for treating and enlarging a tissue, an organ or a cavity. The device is composed of a hollow expanding pouch made of a resorbable material or a perforated material that can be attached to a filling element. The pouch can be filled with a biocompatible materials, one or more times in few days interval, after the insertion of the device. While filling the pouch every few days the tissue expands and the filling material if it is bioactive start to function. The devices allow immediate direct contact between the filling material and the tissue. These devices and methods can be used for example for: horizontal and vertical bone augmentation in the jaws, soft tissue augmentation, fixating bone fractures etc.