Thanks, Ko-Ko, for your interest. I use a combination of several tools. As an example, the first illustration (Nitrate-Nitric Oxide Pathway): the individual image elements (spinach etc.) I created with an AI image generator. You can use practically any image generator out there. The chemical representations of nitrate etc. are open-access elements from chemistry sites, which I run through an image processor to give them the appropriate hues and colours. I combine all elements using the Affinity software packages. I create the charts with Datawrapper, as you can see from the 'credits' line below each chart (but you need the raw data to feed to datawrapper, which you need to extract from the study that has published the data).