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If CLARITY had been devised 15 years ago, my life as a PhD student would have been much, much easier. I was trying to understand how migrating cerebellar granule cells find their way through the developing chicken brain. This involved dissecting hundreds of tiny brains from chick embryos into slices and labeling some of the cells with a fluorescent dye. I'd incubate the slices for a week or so and embed them in a gel. Then, I'd use a machine called a microtome to shave each one into dozens of sections, each thinner than a human hair, mount those onto glass slides and, finally, examine them with a co focal fluorescence microscope.

Tissue sectioning is a time-consuming and laborious process. Once the solidified gel has been glued to the microtome platform, the vibrating blade moves back and forth across it slowly, moving down one microscopic step at a time, to cut a series of sections from one end of the slice to the other. Each section has to be carefully removed with a paintbrush as it comes loose, and then mounted onto a glass microscope slide. CLARITY does away with all this, by making samples of biological tissue completely transparent.

The method, developed by Kwanghun Chung of Stanford University and his colleagues, is described today in the journal Nature. The first step is to inject the tissue with formaldehyde and hydrogels. The formaldehyde cross-links all the molecules inside it, apart from the fats, to each other and to the hydrogel. When heated to body temperature, the tissue and hydrogel harden together to form a hybrid mesh. The fats, which scatter light and blur microscope images, can then be cleared away by applying an electrical current across the tissue sample.

The whole process takes four or five days. The 'clarified' tissue is not only transparent but also retains its original three-dimensional structure, and is permeable to large molecules, so it can be treated with fluorescently-labeled antibodies that label specific proteins or other types of molecular probes. It is also resilient enough to be washed and then stained a second time with other molecular probes, which would be very useful to studying rare tissue samples.

The researchers demonstrated the method on the mouse brain and on small blocks from the frontal lobe of an autistic patient, which had been preserved in a brain bank for more than 6 years. Using various probes, they labeled specific types of neurons in both, and traced the routes of their fibres throughout the samples. The ability to do so on intact brains rather than two-dimensional tissue slices makes the method particularly useful for visualising neural pathways over long distances.

CLARITY can be used on any kind of tissue from any organism, so it could lend itself to many different applications, but seems particularly amenable to developmental studies. Embryonic development involves mass movements of cells not only in the brain but also other parts of the embryo, which requires complex interactions between the cells and their surroundings. Embryos are, of course, three dimensional, so many of these processes are hard to reproduce in experiments on tissue slices. Using CLARITY, developmental biologists can now study them as they occur in their natural environment.


A team at Stanford University has made brains transparent, allowing entire networks of neurons to be highlighted and then viewed through an optical microscope. In the past, it has only been possible to image slices of organs such as the brain. First, Karl Deisseroth and his colleagues propped up the cells in a whole mouse brain using a scaffold of fibrogel, before removing all the fat surrounding the cells. The technique – details of which are published in the latest issue of Nature – also works on human brains, potentially revealing how changes to the connectivity of neurons cause conditions such as autism.

imagen descriptiva
Brain drain
Brain trust
Brain training
Idea o plan original e inteligente
Clínicamente muerto
Fuga de cerebros
Asesores de un líder/jefe
Ejercitar la memoria
Lluvia de ideas
To have something on the brain

To pick somebody's brain

To be a brain box
To be out of your brain (informal)
To be the brains behind/of something

To beat one´s brain out (to do sth)
Estar obsesionado con algo de manera negativa
Averiguar lo que alguien está pensando haciéndole preguntas
Ser una persona muy inteligente
Estar muy bebido
Ser la mente detrás de una organización, sistema
Intentar hacer algo durante mucho tiempo

“The researchers demonstrated the method on the mouse brain and on small blocks from the frontal lobe of an autistic patient, which had been preserved in a brain bank for more than 6 years”.

Relative clauses are used to give additional information about something without starting another sentence. This information can either define something (defining clause), or provide unnecessary, but interesting added information (non-defining clause). By combining sentences with a relative clause, a text becomes more fluent and you can avoid repeating certain words.
- I'd like to buy that beautiful car which is over there.
- That is the school (that) I went to as a boy.

Relative clauses can be introduced by:
- a relative pronoun: who (whom), which, that, whose.
- no relative pronoun: Ø.
- where, why and when instead of a relative pronoun.

Three questioned- tips to consider when deciding which relative pronoun to use:
- Is the subject or object or possessive of a relative clause?
- Does it refer to a person or an object?
- Is the relative clause a defining or non-defining relative clause?

The information provided in a defining relative clause is crucial to understand the meaning of the sentence. The purpose of a defining relative clause is clearly to define who or what we are talking about. Without this information, it would be difficult to know who or what is meant.
- The woman who lives in apartment No. 34 has been arrested.

Relative Pronouns in Defining Relative Clauses
- Children who (that) play with fire are in great danger of harm.
- The man who bought all the books by Hemingway has died.

Generally, who and which are more usual in written English whereas that is frequently used in speech when referring to things.

Relative Pronouns Used As the Object of Defining Relative Clauses
- That's the boy (Ø, that, who, whom) I invited to the party.
- There's the house (Ø, that, which) I'd like to buy.

Relative Pronouns Used As a Possessive In A Defining Relative Clauses
- He's the man whose car was stolen last week.
- They were sure to visit the town whose location (OR the location of which) was little known.

Non-defining relative clauses provide interesting additional information which is not essential to understand the meaning of the sentence.
- Mrs. Jackson, who is very intelligent, lives on the corner.

Correct punctuation is essential in non-defining relative clauses. If the non-defining relative clause occurs in the middle of a sentence a comma is put before the relative pronoun and at the end of the clause. If the non-defining relative clause occurs at the end of a sentence a comma is put before the relative pronoun.

Watch out! In defining relative clauses there are no commas.

Relative Pronouns in Non-Defining Relative Clauses
- Frank Zappa, who was one of the most creative artists in rock 'n roll, came from California.

Relative Pronouns Used As The Object of Non-Defining Relative Clauses
- Frank invited Janet, who (whom) he had met in Japan, to the party.
- Peter brought his favorite antique book, which he had found at a flea market, to show his friends.

'That' can never be used in non-defining clauses.

Relative Pronouns Used As A Possessive In Non-Defining Relative Clauses
- The singer, whose most recent recording has had much success, was signing autographs.
- The artist, whose name he could not remember, was one of the best he had ever seen.

In non-defining relative clauses, which can be used to refer to an entire clause.
- He came for the weekend wearing only some shorts and a t-shirt, which was a stupid thing to do.

Common mistakes and confusing words in English.

Historic / historical
Historic means 'making history or important in history'.
- The landing on the moon was a historic moment.
- This is a historic monument.

Historical means 'related to the study of history'.
- You have done a lot of historical research.

Made from / Made of
Made from is used when the original materials are completely changed during the process of making. It can mean relating to or belonging to someone.
- Paper is made from wood.
- Our food is made from natural ingredients.

Made of is used when the original materials are not completely changed and can still be recognized.
- This chair is made of wood.
- Her purse is made of leather.
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