A method for providing an image of a sample, the method comprising: providing spatially-structured activation radiation having relatively high- and relatively low-intensity regions to a sample that includes phototransformable optical labels PTOLs, the PTOLs being distributed in at least a portion of the sample with a density greater than an inverse of the diffraction-limited resolution volume of imaging optics, and the PTOLs being transformable from an inactivated state wherein the labels radiate little, if any, radiation at a wavelength characteristic of an activated and excited PTOL when exposed to excitation radiation, to an activated state wherein illumination by excitation radiation results in detectable emission of fluorescence radiation, to activate a subset of the PTOLs in the sample located predominately at relatively high intensity regions of the spatially-structured activation radiation; providing spatially-structured excitation radiation to the subset of activated PTOLs in the sample, wherein the excitation radiation is structured so that one or more relatively high intensity regions of the excitation radiation at least partially overlap one or more relatively high intensity regions of the activating radiation; controlling the intensities and spatial structures of the activating radiation and the exciting radiation so that radiation emitted from activated and excited PTOLs in at least one of the overlap regions of relatively high intensity activating radiation and relatively high excitation radiation in the sample is emitted substantially from at least one volume that is comparable to or less than a diffraction-limited resolution volume DLRV of the imaging optics; detecting the fluorescence radiation emitted from the at least one volume by the activated and excited PTOLs with the imaging optics and determining the locations of the activated and excited PTOLs with superresolution accuracy; relocating to a new location within the sample the one or more relatively high intensity regions of the excitation radiation and the one or more relatively high intensity regions of the activating radiation region that overlap; repeating the above steps to determine the locations of more PTOLs within the sample; and combining the determined locations of the different PTOLs to build up a superresolution image of the sample. providing spatially-structured activation radiation having relatively high- and relatively low-intensity regions to a sample that includes phototransformable optical labels PTOLs, the PTOLs being distributed in at least a portion of the sample with a density greater than an inverse of the diffraction-limited resolution volume of imaging optics, and the PTOLs being transformable from an inactivated state wherein the labels radiate little, if any, radiation at a wavelength characteristic of an activated and excited PTOL when exposed to excitation radiation, to an activated state wherein illumination by excitation radiation results in detectable emission of fluorescence radiation, to activate a subset of the PTOLs in the sample located predominately at relatively high intensity regions of the spatially-structured activation radiation; providing spatially-structured excitation radiation to the subset of activated PTOLs in the sample, wherein the excitation radiation is structured so that one or more relatively high intensity regions of the excitation radiation at least partially overlap one or more relatively high intensity regions of the activating radiation; controlling the intensities and spatial structures of the activating radiation and the exciting radiation so that radiation emitted from activated and excited PTOLs in at least one of the overlap regions of relatively high intensity activating radiation and relatively high excitation radiation in the sample is emitted substantially from at least one volume that is comparable to or less than a diffraction-limited resolution volume DLRV of the imaging optics; detecting the fluorescence radiation emitted from the at least one volume by the activated and excited PTOLs with the imaging optics and determining the locations of the activated and excited PTOLs with superresolution accuracy; relocating to a new location within the sample the one or more relatively high intensity regions of the excitation radiation and the one or more relatively high intensity regions of the activating radiation region that overlap; repeating the above steps to determine the locations of more PTOLs within the sample; and combining the determined locations of the different PTOLs to build up a superresolution image of the sample.