Studying thermophiles, microorganisms thriving at high temperatures, provides insights into life's adaptation to extreme conditions. However, observing them *in vitro* requires specialized high-temperature microscopy (HTM). This article introduces laser-assisted HTM (LA-HTM), using gold nanoparticles as efficient, biocompatible light absorbers to achieve microscale heating. The method's effectiveness is demonstrated with *Geobacillus stearothermophilus* and *Sulfolobus shibatae*, showcasing germination, growth, and motility at high temperatures. LA-HTM offers a simple, safe alternative for observing thermophiles using accessible microscopy tools.

Céline Molinaro, Maëlle Bénéfice, Aurore Gorlas, Violette Da Cunha, Hadrien M. L. Robert, Ryan Catchpole, Laurent Gallais, Patrick Forterre, Guillaume Baffou