In this talk, I will give an overview of 3 different aspects of my research: what can we learn from measuring the baryon acoustic oscillations (BAO) in different environments; why are under-dense regions interesting and how can we quickly test departures from GR in void profiles using Monte Carlo Random walks; and finally, I will discuss how we can challenge the LCDM picture by measuring the growth rate in different environments. In particular I will present the first constraint from the void-galaxy cross correlation function in the 6dF Galaxy Survey.