In a FRET experiment using a Src biosensor, the activity level of Src in response to varying amounts of OPN was evaluated based on the conformational change in the Src biosensor.20 In a second FRET experiment using a vinculin force biosensor, the migratory behavior of individual tumor cells was evaluated in which the FRET lifetime increased by stretching a molecular linker in the force sensor.21 Here, SPP1 is linked to neoplasm.