Biophysical stimulation to improve the cardiac tissue models. (A) Cardiac spheroids cultured in microbioreactors and subjected to electrical stimulation at various frequencies. Electrical signals increased expression of gap junction and sarcomere thickness in cardiac spheroids. Adapted from Eng et al. (61) (CC BY 4.0 license) Copyright 2016, The Authors, published by Springer Nature. (B) EHT models stimulated with uniaxial cyclic stretch (10% strain, 1 Hz) using a bioreactor. The expression of gap junction and sarcomere structure and electrical responses were enhanced by mechanical stimulation. Adapted from Massai et al. (63) (CC BY 4.0 license) Copyright 2020, The Authors, published by Frontiers Editorial Office. (C) Ring-shaped EHT models with electrical pulses and stretch conditioning, which showed improved biomechanical properties and electrical coupling. Adapted from Lu et al. (64) (CC BY 4.0 license) Copyright 2021, The Authors, published by Ivyspring International Publisher.