A method of forming a focal plane array by: forming a first wafer having sensing material provided on a surface, which is covered by a sacrificial layer, the sensing material being a thermistor material defining at least one pixel; providing supporting legs for the pixel within the sacrificial layer, covering them with a further sacrificial layer and forming first conductive portions in the surface of the sacrificial layer that are in contact with the supporting legs; forming a second wafer having read-out integrated circuit (ROIC), the second wafer being covered by another sacrificial layer, into which is formed second conductive portions in contact with the ROIC; bringing the sacrificial oxide layers of the first wafer and second wafer together such that the first and second conductive portions are aligned and bonding them together such that the sensing material is transferred from the first wafer to the second wafer when a sacrificial bulk layer of the first wafer is removed; and removing the sacrificial layers to release the pixel, with the supporting legs underneath it.