A microscope assembly for optical imaging of biological tissue that has a high optical scattering coefficient, the assembly comprising: an optical excitation source for irradiating a scan area of a biological tissue sample and generating optical emissions to be emitted from the sample, wherein the sample comprises first and second faces and wherein in use the sample is disposed such that the first face faces away from the excitation source and the second face faces the excitation source; a two dimensional scanning element for scanning the light from the excitation source over the scan area of the sample; a focusing element having a numerical aperture NA 1 disposed to focus light from the excitation source onto the sample; a first optical collection and focusing means disposed to collect light from the first face of the sample, the collected light comprising transmitted light from the excitation source and a first optical emission generated in the sample in response to light from the excitation source, the first optical collection and focusing means having a numerical aperture NA 2 larger than the numerical aperture NA 1 of the focusing element, wherein the first optical emission is a second harmonic optical emission generated in the sample in response to light from the excitation source; a first optical band-pass filter disposed to block the transmitted light from the excitation source; an aperture with an aperture size corresponding to the irradiated area of the sample, the aperture being located for background suppression with respect to the first optical emission at the conjugate image position of the sample generated by the first optical collection and focusing means; and a first optical detector disposed to collect collected light from the first face of the sample for detecting the first optical emission from the scan area of the sample. an optical excitation source for irradiating a scan area of a biological tissue sample and generating optical emissions to be emitted from the sample, wherein the sample comprises first and second faces and wherein in use the sample is disposed such that the first face faces away from the excitation source and the second face faces the excitation source; a two dimensional scanning element for scanning the light from the excitation source over the scan area of the sample; a focusing element having a numerical aperture NA 1 disposed to focus light from the excitation source onto the sample; a first optical collection and focusing means disposed to collect light from the first face of the sample, the collected light comprising transmitted light from the excitation source and a first optical emission generated in the sample in response to light from the excitation source, the first optical collection and focusing means having a numerical aperture NA 2 larger than the numerical aperture NA 1 of the focusing element, wherein the first optical emission is a second harmonic optical emission generated in the sample in response to light from the excitation source; a first optical band-pass filter disposed to block the transmitted light from the excitation source; an aperture with an aperture size corresponding to the irradiated area of the sample, the aperture being located for background suppression with respect to the first optical emission at the conjugate image position of the sample generated by the first optical collection and focusing means; and a first optical detector disposed to collect collected light from the first face of the sample for detecting the first optical emission from the scan area of the sample.