Progress in the culturing of microorganisms that are important to ocean ecology has recently accelerated, and technology has been a factor in these advances. However, rather than a single technological breakthrough, a combination of methods now enable microbiologists to screen large numbers of cultures and manipulate cells that are growing at the low biomass densities that are characteristic of those found in seawater. The value of ribosomal RNA databases has been reaffirmed, as they provide nucleic-acid probes for screening to identify important new species in culture. The new cultivation approaches have focused on specific targets that ecological studies suggest are significant for geochemical transformations, such as SAR11. Here, we review how to cultivate marine oligotrophs and why it is worth the effort.