Table 1.

The major differences of microscale 2D and 3D systems

	microscale 2D system	microscale 3D system
Differences between corresponding macro systems	significantly reduced amount of cells and reagent per endpoint greatly reduced convective motion of molecules diffusion-dominant transport of molecules significantly increased surface-to-volume ratio increased sensitivity of paracrine signaling	significantly reduced amount of cells and reagent per endpoint increased polymerization rate of natural polymers such as collagen I enhanced controllability of collagen fibrous structure similar sensitivity of paracrine signaling
Dominant molecule transport mechanism	diffusion-dominant
Use of ECM proteins	various natural ECM proteins coated or patterned on the surface	various natural and synthetic ECM materials used gradient of biochemical and mechanical properties possible
HTS accessibility	compatible
Imaging and analysis	compatible with various imaging technologies and analysis algorithms that are currently available