Figure 1.

Examples of cell culture phase contrast light microscopy images of D17 canine osteosarcoma cells cultivated as 2D monolayers (a, b) or three‐dimensional (3D) spheroids (c, d). Monolayer cultivated to near confluence after 2 days. Within the monolayer lawn, epithelial‐like cells were mainly observed; occasional spindle‐shaped cells were located within less confluent areas (a). 2D monolayer after 7 days exhibited an extremely dense cell lawn (b). Spheroids developed the characteristic 3D architecture as round‐shaped cell conglomerates within the first 7 days of cultivation (c). After cultivation for 14 days, spheroids exhibited increased diameters with tightly arranged cells (d). Scale bars = 200 μm.