  Table-top extreme ultraviolet (EUV) microscopy offers unique opportunities
for label-free investigation of biological samples. Here, we demonstrate
ptychographic EUV imaging of two dried, unstained model specimens: germlings of
a fungus (Aspergillus nidulans), and bacteria (Escherichia coli) cells at 13.5
nm wavelength. We find that the EUV spectral region, which to date has not
received much attention for biological imaging, offers sufficient penetration
depths for the identification of intracellular features. By implementing a
position-correlated ptychography approach, we demonstrate a millimeter-squared
field of view enabled by infrared illumination combined with sub-60 nm spatial
resolution achieved with EUV illumination on selected regions of interest. The
strong element contrast at 13.5 nm wavelength enables the identification of the
nanoscale material composition inside the specimens. Our work will advance and
facilitate EUV imaging applications and enable further possibilities in life
science.
