  Permutation approach is suggested as a method to investigate financial time
series in micro scales. The method is used to see how high frequency trading in
recent years has affected the micro patterns which may be seen in financial
time series. Tick to tick exchange rates are considered as examples. It is seen
that variety of patterns evolve through time; and that the scale over which the
target markets have no dominant patterns, have decreased steadily over time
with the emergence of higher frequency trading.
