Our understanding of the left atrium (LA) has evolved from a benign chamber innocently positioned next to the more significant left ventricle (LV) to a critically important modulator of left ventricular filling, a volume sensor, and a barometer of diastolic function. It is responsible for the secretion of natriuretic peptides and serves as an important prognostic marker in patients with cardiovascular disease. Dynamic LA mechanics may be assessed with crude 2D speckle-tracking methods, designed for the LV but applied to the LA, and have the potential to offer important insights in patients with heart failure, atrial fibrillation, diastolic dysfunction, and mitral valve disease.