The invention provides useful devices and methods for both studying interfaces between cell membranes, and integrating living cells with synthetic surfaces exhibiting complex lateral composition, organization and fluidity. A system equation for a target medium such as tissue is solved using a Normalized Difference Method. The detector is arranged so as to be visible from the outside of the tank. The section and retainer can be made as a single whole, and spring-loaded by one spring. This server includes a protected content generator which encapsulates an original content to generate a protected content corresponding to the original content, and an accessibility setting unit which sets access right to access the protected content to a user of the content management server.