A novel approach leading to the microscales of complex turbulent flows is reviewed. The approach is illustrated in terms of the classical microscales proposed by Taylor, Kolmogorov, Oboukhov-Corrsin and Batchelor. A thermal mesomicroscale between the Kolmogorov and Batchelor scales,η θ = (η η 2 B ) 1 B , respectively, denote the Kolmogorov and Batchelor scales, ν and α the kinematic and thermal diffusivities, and the rate of turbulent mechanical energy per unit mass. The foundations of the well-known correlation for forced convection over a flat plate,Nu l ∼ Re 3 l Pr 1 l being an integral scale, is interpreted in terms of l, η and η θ .The approach is utilized to construct the microscales of forced and natural diffusion flames. In terms of a flame Batchelor scaleη B = ν β D 2 β 1 β . Here ν β = ν (1 + B) andD β = D (1 + B), respectively, denote the flame momentum diffusivity and the b-property diffusivity, ν and D being the usual diffusivities and B the transfer number. A model for the fuel consumption in forced flames is proposed in terms of η β . The model correlates well with the existing experimental data.For buoyancy driven flames, a Kolmogorov scaleη β ∼ (1 + σ β ) 1 D 3 β B 1 β = ν/D β denotes a flame Schmidt number, B being the rate of buoyant energy production. The limit of this scale for σ β → 0 turns out to be a flame Oboukhov-Corrsin scale,η C ∼ D 3 β B 1 β . The model correlates well with the existing experimental data.For oscillating (on the mean) flows, a Kolmogorov scale,η ∼ (ν 3 / ) 1 1 ] 1