1. A device for tissue characterization, comprising: a structure, formed of a rigid surface configured as a truncated cone, having a first cross-sectional configuration defining a diameter and having a second cross-sectional configuration defining an axis; at least one piston sensor; a first force exerting mechanism, associated with the structure, configured to provide a first force and to cause said first force to be exerted on a tissue, in a direction, along the axis, at an acute angle α to the rigid surface, for fixing the tissue to the structure, so as to immobilize the tissue; and a second force exerting mechanism, associated with the structure, configured to press said at least one piston sensor against an external surface of the immobilized tissue thereby to provide a counter force, and to thereby exert said counter force on the immobilized tissue, wherein the first force exerting mechanism is configured to set at least a component of the force in opposition to at least a component of the counter force, said structure, said first mechanism and said second mechanism combined being configured to force the immobilized tissue against the at least one piston sensor, and further to force the at least one piston sensor against the immobilized tissue, bringing about an effective contact between the at least one piston sensor and the immobilized tissue; and wherein said at least one piston sensor is selected from the group consisting of optical sensor, X-ray sensor, RF sensor, MW sensor, infrared thermography sensor, ultrasound sensor, MR sensor, impedance sensor, temperature sensor, radioactive-emission sensor, mechanical sensor, and a nonirradiative RF sensor.