This work investigates the early stage evolution of thermally nucleated microbubbles in water using in situ high-speed, 400 fps, transmission electron microscopy. A Pt wire Joule heater induced bubble nucleation and growth from air-saturated water at different levels of power. For all powers below Pt breakdown, the dissolved gas initiates bubble nucleation at the concave surface defects adjacent to the area of highest temperature. A combination of interfacial forces and stress relaxation drive rapid migration of the bubbles away from the nucleation site. Thermocapillary forces ultimately dominate and drive their return to the region of highest temperature. The dynamic response highlights the importance of this length and time domain, which has until now received limited direct study.