A window has a pane of transparent material. A first set of microfluidic channels pass through a first area of the pane, and a second set of microfluidic channels pass through a second area of the pane. Microfluidic planes are in fluid communication with the first and second sets of microfluidic channels. A first pump is in fluid communication with the first set of microfluidic channels, and selectively moves a first fluid having a first level of opacity through the microfluidic planes via the first set of microfluidic channels. A second pump is in fluid communication with the second set of microfluidic channels, and selectively moves a second fluid having a second level of opacity through the microfluidic planes via the second set of microfluidic channels. Moving the second fluid into the microfluidic planes pushes the first fluid out of the microfluidic planes, thereby adjusting an opacity of the window.