Fukumura and colleagues used a scanning Hall probe microscope to study the formation of the bubbles. The compound that they studied is unusual in that its magnetic structure changes markedly with temperature. As the temperature drops, the material becomes more antiferromagnetic (that is, the magnetic moments of neighbouring layers point in opposite directions). This effect eventually causes the net magnetic field to fall to almost zero below 37 Kelvin, leaving only a small domain with any trace of a magnetic field. As the temperature is increased, however, these domains increase in size until they form a regular pattern of magnetic bubbles around 72 Kelvin. The bubbles are extremely stable in external magnetic fields because they are small and circular. However, they collapse again when the temperature is increased above 78 Kelvin. The team believes that by changing the composition of the materials, or by fabricating artificial layers in the structure, the bubbles could be made stable at higher temperatures.