Cell internalization is a common biological process by which micro- and nanoparticles are introduced into the cell. The biological mechanisms of internalization are reported for particles well below the mitotic size of the cells and are size [1] and shape-dependent [2]. However, a question arises: Which is the maximum size of an external particle that can be internalized by a specific cell? Although, they are initially curiosity-driven questions, the answers have relevant implications to discover new cellular internalization processes in fundamental cell biology, in the fields of micro- and nanoparticle applications, and in the emerging field of intracellular chips for nanobiomedicine.