Forming holes in a material (1) includes focusing a pulsed laser beam (2) into a laser beam focal line (2b) oriented along the beam propagation direction and directed into the material, the laser beam focal line (2b) generating an induced absorption within the material (1), the induced absorption producing a defect line along the laser beam focal line (2b) within the material (1), and translating the material (1) and the laser beam (2) relative to each other, thereby forming a plurality of defect lines in the material, and etching the material in an acid solution to produce holes greater than 1 micron in diameter by enlarging the defect lines in the material. A glass article includes a stack of glass substrates with formed holes of 1-100 micron diameter extending through the stack.