Building circuits that accurately manipulate individual electron is an ongoing challenge in nanoelectronics. Reliable electron-on-demand source can lead to a new fundamental realization of Ampere and offer avenues to explore the particle limit of electron optics on a chip. Recent experimental progress with so called single-parameter tunable-barrier electron pumps has stimulated the need to develop a practical theory describing the process of charge capture in electrostatically defined quantum dots. I will review recent progress on that front focusing on universal aspects of charge capture dynamics. We show that a simple master equation approach can reveal universal non-thermal counting statistics which is a signature of the strongly non-adiabatic regime. Full quantum mechanical treatment of a single level model predicts additional features, most notably quantum smearing of the dc current quantization step and a coherent manifestation of the dynamical phase of a particle being captured. The latter can be seen as a single-lead Landau-Zener-backtunneling interferometer, that measures quantum beats in spontaneous decay from the quantum dot into the particle-hole continuum.