English: a, Tomographic slice of a cardiac sarcomere M-band depicting thick and thin filaments. Scale bar, 50 nm. b, Reconstructed thick and thin filaments mapped into a tomogram. Thin filaments obstructing the view on the thick filament were removed for clarity. Scale bar, 50 nm c, Structure of the thick filament from the M-band to the C-zone. For clarity, only the first four cMyBP-C stripes are shown here. d, Illustration of the various sarcomere components and their color code which is maintained throughout the manuscript, unless otherwise indicated. TM, tropomyosin. TK domain, titin kinase domain.