Quasi-ellipsoidal IDP U2015-M-1 containing preferentially oriented elongated grains (e.g., grains A–F in panels (b) and (c)). (a) Volume-rendered image of the entire particle from PCXNT data. (b) and (c) Volume-rendered images of internal structure viewed from two different angles. A cluster (dashed rectangle in panel (b)) contains hollow grains, with one indicated by an arrow (see Figure 2(c)). Volume: 0.9 × 2.3 × 3.7 μm³.