1. A method for obtaining a three-dimensional volume image of a sample, the method comprising: obtaining, by dark-field microscopy, a plurality of two-dimensional images from the sample comprising subject particles and at least one cell, biological cellular material or tissue, nonbiological fiber matrix, filter matrix or emulsion, the plurality of two-dimensional images comprising at least one two-dimensional image taken at each of a plurality of equally spaced sample locations along a direction of focus, each two-dimensional image containing both in-focus and out-of-focus light from the sample, wherein: the at least one cell, biological cellular material or tissue, nonbiological fiber matrix, filter matrix or emulsion is fluorescent; the sample comprises at least one unstained subject particle within the at least one cell, biological cellular material or tissue, nonbiological fiber matrix, filter matrix or emulsion, where the at least one unstained subject particle is non-fluorescent; and the dark-field microscopy comprises broadband light combined with specific wavelengths of fluorescence excitation light for illumination of the sample over a narrow range of wavelengths; inputting the plurality of two-dimensional images to a three-dimensional computational method for determining a location of the at least one cell, biological cellular material or tissue, nonbiological fiber matrix, filter matrix or emulsion present in the sample; and formulating a three-dimensional volume image of the sample, the three-dimensional volume image showing a location of the subject particles and the location of the at least one cell, biological cellular material or tissue, nonbiological fiber matrix, filter matrix or emulsion present in the sample.