Surprisingly, the second term, the collective heating, can be dominant, even for a sparse nanoparticle distribution. This is because the long-range temperature diffusion profile around a source of heat decays at 𝛿𝑇 𝑟 ∝ 1 𝑟 ⁄ , where r is the distance from the heat source. Therefore, the contribution of the collective heating is determined by the number of particles and their interdistances in the illuminated area. The global temperature at the center of the laser beam can be estimated using the analytical equations of the theoretical model developed by Baffou et al. The prediction of the temperature increase (ΔTglobal) using this model was validated by comparison with numerically simulated temperature and the experimentally measured 𝛥𝑇 using a quadriwave shearing interferometry (QSI) designed to measure temperature distribution around nanometric heat sources , optical hydrogen nanothermometry , and XRD 84 , respectively. For example, the predicted ΔTglobal using infinite lattice (Figure of Baffou et al.) was consistent with the measurements for a sample consisting of uniformly distributed lithographic Au nanoparticles covering a whole one-inch glass substrate.