Baryon density parameters in bound objects (left) and the IGM (right) as function of redshift for cold (solid lines), warm (dotted lines), hot (short-dashed lines), stellar (dot-dashed lines with asterisks), HI (long-dashed lines), and H₂ (dot-dot-dot-dashed lines) phases. The horizontal grey line marks the value of Ω_0, b. Stars form out of cold gas that dominates the baryon budget at z ≳ 6 and is overtaken by warm gas at later times.