We summarize our work on structures in different stages of aggregation, and spanning a wide range in redshift. We emphasize our work on high resdhift clusters. This comprises the analysis of ~ 7 square degrees using deep images with several broad-band optical filters. We plan to complement these with near IR observations in 4 m class telescopes. Preliminary results of the analysis in a field of 35 × 35 arcmin2 indicate the detection of several candidates to be clusters at redshifst z > 0.5. When all the fields are analyzed, we will have an adequate sample for future detailed studies with the GTC.