AGNES
In steps one all the data points are assigned as clusters. In step two again depending upon the density and distances the points are clubbed into a cluster. Lastly, in step 3 all the similar points depending upon density and distances are clustered together which are distinct to other clusters thus forming final clusters.
AGNES is an inside-out or bottoms-up approach. Here every data point is assigned as a cluster initially if there are n data points n clusters will be formed initially. In the next iteration, similar clusters are merged (again based on the density and distances), this continuous until similar points are clustered together and are distinct for other clusters.