Abstract: Bioreactors and methods of using them to produce tissue engineered products or culture cells are disclosed, and more particularly on the development of a tissue and cell culture method based upon an expanded bed bioreactor in which an initial resting bed of particles on which or in which cells are attached, encapsulated or immobilised have a fluid passed upwards through the bed to form an expanded bed in which the fluid acts to separate the particles, i.e. under plug flow conditions to enable the relative positions of the particles to be maintained during the step of culturing the cells to form tissue and helps to reduce collisions between particles and turbulent flow or convective mixing.