An exciting left-arm bowler of express pace, Mills has had a dramatic rise through the ranks after only starting to play cricket at the age of 14.
He made his first-class debut for Essex in June 2011 against the touring Sri Lankans and claimed the wicket of Tharanga Paranavitana.
Having already represented his country at under-19 level at the beginning of the year, he then took on Sri Lanka A in August as part of an England Development XI.
By the end of the summer, he had also featured in three LV= County Championship matches and one Clydesdale Bank 40 fixture for Essex.
He became a potential England Performance Programme player in September but next month was promoted to the main EPP party as an injury replacement and toured Bangladesh with England Lions.
Mills returned career-best figures of 4-25 against Glamorgan in May 2012, taking 4-4 in a spell of 31 balls.
Despite a quiet 2013 - Mills took 11 wickets in six championship appearances - his similarity to Mitchell Johnson made him an England net bowler in the early part of the Ashes tour, which he followed by shining for the EPP in Australia.