According to examples, an apparatus may include an array of micro-mirrors, each of the micro-mirrors being individually controllable to selectively be in a first position or a second position, and a light source to direct a pulse of light onto the array of micro-mirrors with sufficient intensity to cause micron-sized particles on a powder bed upon which the light is directed from the array of micro-mirrors to at least partially melt. Each of the micro-mirrors that is in the first position may reflect light onto a respective area on a layer of micron-sized particles to at least partially melt the micron-sized particles in the respective area and each of the micro-mirrors that is in the second position may reflect light away from the powder bed on which the micron-sized particles are supported.