Rechargeable metal batteries have been considered as one of the most promising techniques to meet the fast-growing demand of high-energy-density battery systems for modern electrical devices. Zn metal batteries (ZMBs) are among strong candidates due to their relatively high theoretical capacity (820 mAh g^-1), lower cost and better safety. Especially, the stability of Zn metal in water endows ZMBs with capability of usage in aqueous electrolytes, which makes them nontoxic and more eco-friendly. Practical application of aqueous ZMBs is seriously suffering from the severe growth of Zn dendrites. Many strategies have been developed to solve this problem and adding additives into electrolytes is found to be one of most facile and effective methods. However, the mechanisms of dendrite growth and roles of these additives in directing uniform Zn deposition are not fully understood. Some operando imaging techniques, such as in-situ optical microscopy and X-ray computed tomography, have been utilized to study the growth of Zn dendrites in electrolytes, but the nucleation and initial growth are very difficult to be seen due to the limitation of resolution. Herein, we investigated the electrodeposition behaviours of Zn in different electrolytes at the nanoscale by utilizing the in-situ liquid cell transmission electron microscopy (TEM) technique. The nucleation and growth of Zn dendrites in 2M ZnSO₄ aqueous electrolyte under different current densities were studied first. It was observed that the Zn particles were generated at the edge of the Pt electrode after the plating started, and gradually grew into Zn flakes which randomly stood on the edge of the electrode. In addition, some of the newly deposited Zn were found to preferably grow from the edges of the previously deposited flakes, evolving into a shape of “daisy-chain” subsequently. This electrodeposition behaviour, resulting from the “tip effect”, reveals a formation mechanism of Zn dendrites in the mild aqueous electrolyte. LiCl has been reported to be an effective additive to alleviate the formation of zinc dendrites, but the underlying mechanism remains to be unclear. Therefore, 2M LiCl was introduced into the electrolyte as the additive. Interestingly, significant differences in the electrodeposition behaviour were observed, that the deposited Zn flakes aggregated and grew into blocks instead of forming dendrites with the “daisy-chain” structure. This behaviour can be explained by the favoured nucleation on the planar surface of the deposited Zn flakes, as the edges of them were isolated by Li ions due to the electrostatic shielding effect. The SEM images of the electrodes after the symmetric Zn||Zn open-cell tests also confirmed this electrodeposition preference.