There is described an isolated 3-dimensional liver spheroid wherein said spheroid has: increased ATP content as compared to a 3-dimensional liver spheroid cultured in Complete William's E medium alone; the same or increased activity of cytochrome P450 1A1 and cytochrome P450 1B1 as compared to a 3-dimensional liver spheroid cultured in Complete William's E medium alone; and increased albumin secretion as compared to a 3-dimensional liver spheroid cultured in William's E medium alone.