ALMA is an astronomical interferometer of innovative design, initially composed of 66 high-precision antennas and operating at wavelengths of 0.3 to 3.6 mm. Its main array will have 50 antennas acting as a single interferometer. An additional compact array of four 12-metre and twelve antennas is also planned. The antennas can be arranged across the desert plateau over distances from 150 metres to , which will give ALMA a variable "zoom". The array will be able to probe the universe at millimetre and submillimeter wavelengths with unprecedented sensitivity and resolution, with vision up to ten times sharper than the Hubble Space Telescope. These images will complement those made with the VLT Interferometer. ALMA is a collaboration between East Asia (Japan and Taiwan), Europe (ESO), North America (USA and Canada) and Chile.