Simulation techniques have resulted in significant progress in elucidating phenomena that are too fast and small for direct observation; however, there has also been considerable progress in the legacy techniques of direct observation. We have been studying applications of microbubbles for ultrasonically enhanced drug delivery, and in this presentation, we will introduce our results of high-speed observations carried out to elucidate the roles of microbubbles injected into the capillaries of living tissues. Micron-sized bubbles stabilized by a lipid shell were introduced into a limen of 10 microns in diameter created in acrylamide gel, and their dynamics under the conditions of exposure to 1-MHz short-pulsed ultrasound was observed using a high-speed video camera (HPV-X2, Shimadzu, Japan) equipped in a microscope (ECLIPSE Ti, Nikon, Japan) with an objective lens (Plan APO IR 40x, Nikon, Japan). The camera captured 256 frames at a framing rate up to 10 Mfps to visualize bubble dynamics inside a narrow capillary that will lead to ultrasound-enhanced extravasation. Oscillation of a water droplet of a few millimeters in size in air, which is the opposite situation of bubble oscillation in water, will also be discussed in this presentation.