In Plato's eponymous dialogue, Timaeus, the main character presents the universe as an almost perfect sphere filled by tiny invisible particles having the form of four regular polyhedrons. At first glance, such a construction may seem close to an atomic theory. However, one does not find any text in Antiquity tying Timaeus' cosmology to the atomists, and Aristotle made a clear distinction between Plato and the latter. Despite the cosmology in the Timaeus is so far apart from the one of the atomists, Plato is commonly presented in contemporary literature as some sort of atomist, sometimes as supporting a so-called form of 'mathematical atomism'. The problem is that the term 'atomism', and even more so 'mathematical atomism', is rarely defined when applied to Plato. Since, it covers many different theories, there are almost as many different meanings as different authors. The purpose of this article is to consider whether it is right to connect Timaeus' cosmology to some kind of 'atomism', whatever the meaning attributed to 'atomism'. Thus, its purpose is double: to have a better understanding of the cosmology of the Timaeus, but also to consider the different modern 'atomistic' interpretations of this cosmology. Indeed, we would like to show that such a claim, in any form whatsoever, is misleading, and an impediment to the understanding of the dialogue, and more generally of Plato's philosophy.