Diatomite nanoparticles are considered a valid alternative to the synthetic porous silica ones for nano‐based drug delivery systems. In article number 1800247, Luca De Stefano, Claudia Tortiglione, and co‐workers explore the in vivo toxicity of hybrid diatomite nanovectors (DNPs) in a living model organism, the cnidarian freshwater polyp Hydra. The long‐term effects of DNPs on Hydra, based on multiple toxicity endpoints (morphology, growth rate, apoptosis, genetic analysis), demonstrate the in vivo biosafety of this naturally derived material.