Myofilaments are bundled together to make a myofibril.
Myofibril Myofibril is a basic rod like unit of a muscle cell. Muscles are composed of tubular cells called myocytes. These cells in turn contain many chains of myofibrils. Myofibrils are composed of long proteins including actin, myosin and titin.
Myofilaments The long proteins that hold the myofibrils together are organised into thick and thin filaments. These are called myofilaments. These repeat along the length of the myofibrils in sections called as sarcomeres.
Muscles contract by sliding myosin ( thick) and actin ( thin ) filaments along each other.