ACTAR is a new active target/time-projection chamber, designed for reaction and decay studies with nuclei far from stability. This class of instruments, initially developed for high-energy physics, has found profitable applications in medium- and low-energy nuclear physics as shown by a successful series of experiments. ACTAR builds on this experience to go beyond, incorporating developments in gas detector technology and a newly-designed electronic system of unprecedented scale in our research domain, to exploit the opportunities offered by the upcoming radioactive ion beams facilities.