Images of a frozen-hydrated algae cell (Chlamydomonas reinhardtii) obtained using the BNP. (a) Differential phase contrast image showing some cell ultrastructure. (b) X-ray fluorescence images showing the distributions and the overlay of zinc (Zn), iron (Fe) and potassium (K). The count levels (minimum to maximum range in counts s−1) are 0–714 for Zn, 0–378 for Fe and 0–899 for K. The algae sample was plunge frozen in liquid ethane and stored in liquid nitrogen for several weeks before examination by the BNP. The images were acquired using fly-scan mode (continuous motion in the horizontal direction) with 35 nm step size and 250 ms dwell time per pixel. One of diffusible ions, K, shows a slightly uneven distribution in the cell demonstrating good cryogenic sample preparation and handling. The fluorescence maps were created by performing peak area fitting for every pixel. (c) The summed spectrum of the whole map with major peaks labeled. While the Kα lines are labeled with element symbols only, the Kβ lines are indicated using `Kb' in the graph.