The next observational frontier to probe the Epoch of Reionization (EoR) is the 21 cm radiation. Radio-telescopes like the Square Kilometer Array (SKA) will enable us to measure this radiation in the form of lightcones for the first time. These observations will reveal the spatial fluctuations of neutral hydrogen during the EoR, as well as allow us to recover the so-called ionised bubbles. In this talk, I will show how we can use topological features to understand the reionisation process and constrain cosmological parameters. Firstly, I will focus on the instant of reionisation of the gas at any point in a field called the reionisation time field (treion) that can be reconstructed from the 21 cm signal using deep neural network. Reionisation sources, ionisation fronts, ionised bubbles, neutral regions and percolation are linked to measurable statistics in treion, which is Gaussian at large scales. Then, following an Alcock-Paczynski test, I will show how we can use the ionised bubbles as standard spheres to put new constraints on the product of the angular diameter distance and the Hubble rate at EoR redshifts which will extend the reach of other cosmological probes to this unexplored era.