A bioreactor (1) for the culture of cells (C) comprising a stack of carriers (7) for cell (C) adherence and liquid medium (M) distribution. The carriers (7) are stacked so as to define levels (6) between adjacent carriers (7) for the flow of the liquid medium (M). Adjacent levels (6) are fluidly interconnected via open spaces (2) so that the liquid medium (M) can flow from one level (6) to an adjacent level (6). The open spaces (2) between a first and an adjacent second level (6′) do not overlap with the one or more open spaces (2) between the second level (6′) and an adjacent third level (6″). One or more of the carriers may also include an area adapted to prevent cell adhesion or growth, thereby allowing for the viewing of cell growth on adjacent carriers from a vantage point external to the bioreactor. Related methods are also disclosed.