Transmission electron microscopy provides unsurpassed structural and compositional information for solid samples, but it is a challenge to image liquid samples in the vacuum of the microscope. I will describe experimental approaches to imaging water and other liquids in the TEM, developed over the last few years, and show how dynamic observations in liquids can produce unique information on electrochemical processes such as deposition and corrosion, crystal growth, and fluid dynamics. I will also discuss the challenges of imaging liquid samples, in particular the problem of understanding and quantifying the effect of the electron beam on the sample. I will conclude with a discussion of ongoing experimental advances that enable us to access a broader range of phenomena. I hope to convince you that TEM of liquids can address grand challenge questions and provide a unique view of structures in liquids and liquid-mediated processes.