The tiny nanospheres shown in the scanning electron microscope are spores of a puffball, a fungus genus from the mushroom-like order.
Because of their uniform size and shape retention after carbonization, researchers are considering their use as nano-biocarbon. E.g., in supercapacitors (Hariram et al., 2021). Or as a standard reference in monodisperse aerosols (Zhirnov et al., 2019).

Puffball spores to measure in strucTEM-Measure:
https://www.structem.eu/tools/measure/?lang=en&id=205-strucTEM-Phenom_989-pilz-bovis

Source data:
Hariram, Muruganandham, et al. “Novel puffball (Lycoperdon Sp.) spores derived hierarchical nanostructured Biocarbon: A preliminary investigation on thermochemical conversion and characterization for supercapacitor applications.” Materials Letters 291 (2021): 129432.
Zhirnov, Anatoliy A., et al. “Spores of puffball fungus Lycoperdon pyriforme as a reference standard of stable monodisperse aerosol for calibration of optical instruments.” PloS one 14.1 (2019): e0210754.