Can a fraction of an IOTA be used? Currently 1 Iota is only worth 2.5 Millionths of a dollar. Imagining IOTA token being used for microscopic transactions can an IOTA be divided?
Currently, 1 IOTA (not MIOTA) is the smallest usable unit and it is not divisible.
However, in the (admittedly) unrealistic case that the value of 1 IOTA increases too much be useful for micro transactions, it is possible to effectively add extra decimal places by artificially increasing the overall supply (see e.g. this link for an instance when this happened).