Explore magnetic reconnection and plasmoid instability in an hour-long lecture by Pallavi Bhat from the International Centre for Theoretical Sciences. Delve into the fundamental plasma physics phenomenon relevant to laboratory, space, and astrophysical systems. Learn about the Sweet-Parker model, tearing mode instability, and the semi-collisional regime. Examine theoretical predictions and numerical simulations using a reduced gyrokinetic model. Discover how plasmoid instability arises at lower, experimentally accessible Lundquist numbers. Gain insights into the reconnection phase diagram, simulation setups, and validation of the semi-collisional regime. Investigate current sheet scaling, wavenumber scaling, and the potential for observing plasmoids in experiments at low Lundquist numbers. Conclude with a summary of findings and future research directions in this critical area of plasma physics.