Muscle or mosaic?
This image by Francesc Sànchez Corredera, from Esther Barreiro’s lab on Molecular mechanisms of lung cancer predisposition (IMIM-Hospital del Mar), is a 3m thick sample of a Guinea pig diaphragm muscle, dyed with an Anti-Myosin Type II antibody and amplified 20 times. The protein myosin II is expressed in fast muscle fibres, but not in slow ones. This is why in this image we can see the fast muscle fibres in which myosin II is present dyed in brown, while the slow muscle fibres are negative (not dyed and therefore white).
This way, researchers can count the number of fibres of each type and establish a fibrilar percentage of each muscle.