  In this paper, we review the recent developments in the field of
buoyancy-driven turbulence. Scaling and numerical arguments show that the
stably-stratified turbulence with moderate stratification has kinetic energy
spectrum $E_u(k) \sim k^{-11/5}$ and the kinetic energy flux $\Pi_u(k) \sim
k^{-4/5}$, which is called Bolgiano-Obukhov scaling. The energy flux for the
Rayleigh-B\'{e}nard convection (RBC) however is approximately constant in the
inertial range that results in Kolmorogorv's spectrum ($E_u(k) \sim k^{-5/3}$)
for the kinetic energy. The phenomenology of RBC should apply to other flows
where the buoyancy feeds the kinetic energy, e.g. bubbly turbulence and
fully-developed Rayleigh Taylor instability. This paper also covers several
models that predict the Reynolds and Nusselt numbers of RBC. Recent works show
that the viscous dissipation rate of RBC scales as $\sim \mathrm{Ra}^{1.3}$,
where $\mathrm{Ra}$ is the Rayleigh number.
