A reusable sample-holding device for readily loading very small wet samples for observation of the samples by microscopic equipment, in particular in a vacuum environment. Embodiments may be used with a scanning electron microscope (SEM), a transmission electron microscope (TEM), an X-ray microscope, optical microscope, and the like. For observation of the sample, embodiments provide a thin-membrane window etched in the center of each of two silicon wafers abutting to contain the sample in a small uniform gap formed between the windows. This gap may be adjusted by employing spacers. Alternatively, the thickness of a film established by the fluid in which the sample is incorporated determines the gap without need of a spacer. To optimize resolution each window may have a thickness on the order of 50 nm and the gap may be on the order of 50 nm.