<p>SEM images of mono-cultured spheroids cultured for (A) 3 days, (B) 9days and co-cultured spheroids cultured for (C) 3 days and (D) 9 days. Scale bars, 10 µm. Immunostaining for AE-2 (green) and actin (red) in (E) mono-cultured spheroids and (F) co-cultured spheroids cultured for 9 days. Scale bars, 50 µm. Scanning electron microscopy images of sectioned co-cultured spheroids cultured for (G) 3 days and (H) 9days. Inner structure of co-cultured spheroids is porous which involves good diffusion of nutrient and oxygen into the spheroid. Scale bars, 10 µm.</p
